Remove the unnecessary backward compatible stuff

[ArcturusZhang]

Description

Last time in the PR in typespec repo to remove the "literal context", I left a workaround to reduce the amount of changes of the PR in this repo.
Now, since that PR has been finished, we could remove that workaround and there should be no code changes, changes will only be in the tspCodeModel.json file.

Checklist

To ensure a quick review and merge, please ensure:

• The PR has a understandable title and description explaining the why and what.
• The PR is opened in draft if not ready for review yet.
  • If opened in draft, please allocate sufficient time (24 hours) after moving out of draft for review
• The branch is recent enough to not have merge conflicts upon creation.

Ready to Land?

• Build is completely green
  • Submissions with test failures require tracking issue and approval of a CODEOWNER
• At least one +1 review by a CODEOWNER
• All -1 reviews are confirmed resolved by the reviewer
  • Override/Marking reviews stale must be discussed with CODEOWNERS first