Fix running all test-all jobs outside PRs (#55917)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55917

As a defensive initial design, conditional Android/iOS job runs for `test-all` were intended to be scoped to PRs only, however required a missing `== 'true'` match specifier.

Fixing this will help us catch rare integration-conflict failures on `main`, at the appropriate commit.

Changelog: [Internal]

Reviewed By: cortinico

Differential Revision: D95042221

fbshipit-source-id: ffa23651c9b8c18939ccbd7ab2279243690944d2