[rfw] Remove the RFW WASM example

[loic-sharma]

package:wasm has been discontinued for years. See: https://github.com/dart-archive/wasm#status-discontinued

This RFW WASM example app was run in customer tests. Its dependency on a very old version of package:ffi causes dependency resolution problems.

In the future, we can re-add a similar example using Dart dynamic modules, once that feature is shipped.

Relevant Discord discussion: https://discord.com/channels/608014603317936148/1177335257574420592/1385010418656743605

Version exemption reason: PRs only affects unpublished parts of example apps.

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.

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

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