[tcgc] remove deprecated description and details

[iscai-msft]

Clear and concise description of the problem

We've switched to doc and details (pr here). After merging this, we want to remove doc and details in our subsequent release

Checklist

• Follow our Code of Conduct
• Check that this issue is about the Azure libraries for typespec. For feature request in the typespec language or core libraries file it in the TypeSpec repo
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.