Changes to phpunit.unit.xml do not trigger backend CI workflows

[Kumar-s75]

Steps to reproduce

1. Open .github/changes-filters.yml on the current main branch.
2. Compare the unit-test configuration entry with the actual file name.
3. Create a pull request that changes only phpunit.unit.xml.

The backend filter currently watches:

- 'phpunit.unit'

The actual file is named phpunit.unit.xml.

Expected behavior

Changes to phpunit.unit.xml set the backend filter output to true and trigger the relevant PHP CI jobs.

Actual behavior

phpunit.unit.xml does not match any path in the backend filter. A pull request changing only that configuration can therefore skip the backend-gated PHP tests, Psalm, PHP lint, and PHP code-style jobs.

Calendar app version

Current main (6.7.0-dev.1)

Suggested fix

Replace:

- 'phpunit.unit'

with:

- 'phpunit.unit.xml'