Update ClientSettingsPolicy future work section

[kate-osborn]

Proposed changes

Update the ClientSettingsPolicy future work section to include supporting attaching to GRPCRoutes and adding HTTP/2 and HTTP/3 directives.

Problem: The ClientSettingsPolicy didn't address GRPCRoute attachment or HTTP/2 and HTTP/3 directives.

Solution: Add GRPCRoute attachment and HTTP/2 and HTTP/3 directives to the future work section of the ClientSettingsPolicy.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

NONE