Bumps pyyaml from 5.1.2 to 5.4.1.

Sourced from pyyaml's changelog.

5.4.1 (2021-01-20)

• yaml/pyyaml#480 -- Fix stub compat with older pyyaml versions that may unwittingly load it

5.4 (2021-01-19)

• yaml/pyyaml#407 -- Build modernization, remove distutils, fix metadata, build wheels, CI to GHA
• yaml/pyyaml#472 -- Fix for CVE-2020-14343, moves arbitrary python tags to UnsafeLoader
• yaml/pyyaml#441 -- Fix memory leak in implicit resolver setup
• yaml/pyyaml#392 -- Fix py2 copy support for timezone objects
• yaml/pyyaml#378 -- Fix compatibility with Jython

5.3.1 (2020-03-18)

• yaml/pyyaml#386 -- Prevents arbitrary code execution during python/object/new constructor

5.3 (2020-01-06)

• yaml/pyyaml#290 -- Use is instead of equality for comparing with None
• yaml/pyyaml#270 -- Fix typos and stylistic nit
• yaml/pyyaml#309 -- Fix up small typo
• yaml/pyyaml#161 -- Fix handling of slots
• yaml/pyyaml#358 -- Allow calling add_multi_constructor with None
• yaml/pyyaml#285 -- Add use of safe_load() function in README
• yaml/pyyaml#351 -- Fix reader for Unicode code points over 0xFFFF
• yaml/pyyaml#360 -- Enable certain unicode tests when maxunicode not > 0xffff
• yaml/pyyaml#359 -- Use full_load in yaml-highlight example
• yaml/pyyaml#244 -- Document that PyYAML is implemented with Cython
• yaml/pyyaml#329 -- Fix for Python 3.10
• yaml/pyyaml#310 -- Increase size of index, line, and column fields
• yaml/pyyaml#260 -- Remove some unused imports
• yaml/pyyaml#163 -- Create timezone-aware datetimes when parsed as such
• yaml/pyyaml#363 -- Add tests for timezone

5.2 (2019-12-02)

• Repair incompatibilities introduced with 5.1. The default Loader was changed, but several methods like add_constructor still used the old default yaml/pyyaml#279 -- A more flexible fix for custom tag constructors yaml/pyyaml#287 -- Change default loader for yaml.add_constructor yaml/pyyaml#305 -- Change default loader for add_implicit_resolver, add_path_resolver
• Make FullLoader safer by removing python/object/apply from the default FullLoader yaml/pyyaml#347 -- Move constructor for object/apply to UnsafeConstructor
• Fix bug introduced in 5.1 where quoting went wrong on systems with sys.maxunicode <= 0xffff yaml/pyyaml#276 -- Fix logic for quoting special characters
• Other PRs: yaml/pyyaml#280 -- Update CHANGES for 5.1

• ee37f46 5.4.1 release
• 2b37f15 Fix stub compat with older pyyaml versions that may unwittingly load it
• 58d0cb7 5.4 release
• a60f7a1 Fix compatibility with Jython
• ee98abd Run CI on PR base branch changes
• ddf2033 constructor.timezone: _copy & deepcopy
• fc914d5 Avoid repeatedly appending to yaml_implicit_resolvers
• a001f27 Fix for CVE-2020-14343
• fe15062 Add 3.9 to appveyor file for completeness sake
• 1e1c7fb Add a newline character to end of pyproject.toml
• Additional commits viewable in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot merge will merge this PR after your CI passes on it
• @dependabot squash and merge will squash and merge this PR after your CI passes on it
• @dependabot cancel merge will cancel a previously requested merge and block automerging
• @dependabot reopen will reopen this PR if it is closed
• @dependabot close will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually
• @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
• @dependabot use these labels will set the current labels as the default for future PRs for this repo and language
• @dependabot use these reviewers will set the current reviewers as the default for future PRs for this repo and language
• @dependabot use these assignees will set the current assignees as the default for future PRs for this repo and language
• @dependabot use this milestone will set the current milestone as the default for future PRs for this repo and language
• @dependabot badge me will comment on this PR with code to add a "Dependabot enabled" badge to your readme

Additionally, you can set the following in your Dependabot dashboard:

• Update frequency (including time of day and day of week)
• Pull request limits (per update run and/or open at any time)
• Out-of-range updates (receive only lockfile updates, if desired)
• Security updates (receive only security updates, if desired)