[file_selector] Update Pigeon in Android implementation

[stuartmorgan-g]

Updates file_selector_android to Pigeon 26.x.

Fixes a latent bug in pigeons/file_selector_api.dart; it had a class that was marked as implements Exception; in older versions of Pigeon this was ignored, so was a no-op, but in current versions it triggers the very limited subclassing support, which doesn't allow inheriting from outside the interface definition, and thus generates incorrect code.

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• 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 linked to 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 I have commented below to indicate which version change exemption this PR falls under¹.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

Footnotes

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[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing. If you believe this PR qualifies for a test exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!). The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.

[gemini-code-assist]

Code Review

This pull request updates the file_selector_android package to use Pigeon version 26.x. The changes primarily consist of regenerating the platform communication code based on the updated dependency. A key fix is the removal of implements Exception from the FileSelectorNativeException class in the Pigeon definition file, which addresses a code generation issue in the new Pigeon version. The pubspec.yaml and CHANGELOG.md files have been updated accordingly. The changes are correct and well-contained, and I have no further feedback.