Update `IssuesService.updateComment` to use `PATCH` instead of `POST` (…

…#437)

* Update IssuesService.updateComment to use PATCH instead of POST

* Acknowledge change in changelog and prepare for release

Fix Issue.isOpen and Issue.isClosed getters (#398)

* Update issues.dart

* require dart 3.0; update to the latest package:lints (#399)

* require dart 3.0; update to the latest package:lints

* update pubspec and changelog

* update the pubspec version; add a changelog entry

require dart 3.0; update to the latest package:lints (#399)

* require dart 3.0; update to the latest package:lints

* update pubspec and changelog

Make `User` field nullable in `PullRequestReview` (#383)

* Make `User` field nullable in `PullRequestReview`

* Rev version

Update MiscService.getApiStatus to v2 (#393)

* v1 has been deleted

Co-authored-by: Rob Becker <rob.becker@workiva.com>

prep 9.20.0

prep 9.19.0