chore: update language server to v6.6.1

Description

Updates the Language Server to the latest version, v6.6.1

gitlab-org/editor-extensions/gitlab-lsp!809 (merged)

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