Use the real discovery reply in the TD21 fixture

Follow-up to #1786. I said there that the TD21 doesn't answer UDP discovery, and that was wrong: it was asleep during my first attempt, and I had skipped discovery in dump_devinfo by passing the family flags. The doorbell does answer, from port 20004.

Changes

• tests/fixtures/smartcam/TD21(EU)_2.0_1.1.5.json: replaces the hand-written discovery_result with the real, redacted reply (from dump_devinfo --host ...). The _comment marker is removed since nothing in the fixture is hand-made any more. The device state is re-recorded at the same time, so the rest of the fixture changes slightly (battery, clock, Wi-Fi scan).
• tests/discovery_fixtures.py: the discovery mock now mirrors the fallback from Discovery: accept cameras that only send the encrypt_type list #1770.

Why a test helper change

The real reply has no encrypt_info and no encryption type in mgt_encrypt_schm, only the top-level encrypt_type: ["3"]. Discover._get_connection_parameters already handles that shape (#1770), but the mock derived the encryption type without the fallback and got None, which failed seven TD21 tests (test_discover_single, test_discover_try_connect_all, test_list_devices, test_list_update_failed). This is the first fixture with that reply shape. The helper change is four lines and does nothing for other fixtures.

Testing

• All tests parametrized on the TD21 pass (108 passed, 2 skipped).
• test_discovery.py, test_device_factory.py and test_devtools.py pass across all fixtures (3970 passed).
• ruff, ruff format and mypy are clean on the changed files.