[Piinks]

The skia-flutter-autoroll and DartDevtoolWorkflowBot are inactive and have been removed form the Flutter org. This cleans them up, removing them from cocoon infra.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read the Flutter Style Guide recently, and have followed its advice.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[gemini-code-assist]

Code Review

This pull request removes the inactive bot accounts skia-flutter-autoroll and DartDevtoolWorkflowBot from the configuration and test files across both app_dart and auto_submit services. The feedback suggests further cleanup by removing a redundant check for engine-flutter-autoroll in pull_request_manager.dart and checking for potential leftover references to skia-flutter-autoroll in ci_successful.dart.