[file_selector] Remove unused web code

[stuartmorgan-g]

The web_helpers.dart file was a helper for an inlined version of cross_file that was originally part of this package. When the inline version was replaced with an import of cross_file, when that was split into its own package, this file wasn't cleaned up, so it was dead 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

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩² ↩³

[stuartmorgan-g]

CHANGELOG/version override: since this is removing non-exported code that nothing was importing internally, it's a no-op.

[gemini-code-assist]

Code Review

This pull request removes the file packages/file_selector/file_selector_platform_interface/lib/src/web_helpers/web_helpers.dart. This file contained web-specific helper functions (createAnchorElement, addElementToContainerAndClick, ensureInitialized) that are no longer used. This change correctly removes dead code, resulting in a cleaner codebase.