Remove HTTP compression experimental flags

[adriansmares]

Summary

References #6699

Changes

• Remove HTTP compression experimental flags. Their behavior was already enabled-by-default, so this only cleans up the codebase.

Testing

N/A. No manual testing is required.

Regressions

N/A. There are no semantical changes from existing behavior, and we did not observe any issues caused by compression (outside of a slight increase in memory usage).

Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• Documentation: Relevant documentation is added or updated.
• The steps/process to test this feature are clearly explained including testing for regressions.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.