fix: sync supported languages with language server

Description

Removes languages that aren't supported by all our models. Brings the Web IDE in line with the Language Server.

The two lists should now be in sync.

Notes:

• This will require a Web IDE release to take effect.
• We should update the docs to reflect the new state, ideally timed with the Web IDE update in the monolith that first includes this change.
• See gitlab-org/editor-extensions/gitlab-lsp#266 (comment 1960216846) for discussion.
• See #1122 (comment 1960391289) for further discussion.

Related Issues

Issue: #1122

How has this been tested?

Screenshots (if appropriate)

What CHANGELOG entry will this MR create?

• fix: Bug fix fixes - a user-facing issue in production - included in changelog
• feature: New feature - a user-facing change which adds functionality - included in changelog
• BREAKING CHANGE: (fix or feature that would cause existing functionality to change) - should bump major version, mentioned in the changelog
• None - other non-user-facing changes