Turn off setup-dart's problem matcher inside the setup action

It registers a matcher file relative to the calling action's folder, which
does not exist in a composite action, and failed every Flutter job.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
e9c9eb75b6Dara Adedeji committed on 9/28/2026, 4:30:29 PMparent6defae8
1 file changedLine totals unavailable