[ci][go_router] Bumps Flutter master version and removes unused BuildContext implementation

[bparrishMines]

BuildContext.dependOnInheritedElement has been removed, so this breaks the implementation of BuildContext. Since the class isn't used anyway, this just deletes it.

Analyzing go_router...
  error - test/test_helpers.dart:227:19 - 'DummyBuildContext.dependOnInheritedElement' ('InheritedWidget Function(InheritedElement, {Object aspect})') isn't a valid override of 'BuildContext.dependOnInheritedElement' ('InheritedWidget Function(InheritedElement, {Object? aspect})'). - invalid_override
           - The member being overridden at test/test_helpers.dart:336:86770.

Fix to roller failure in #2914

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.
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• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I listed at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
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• 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.

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[stuartmorgan-g]

LGTM

[chunhtai]

LGTM