[clang-tools-extra] [clangd] Enforce SymbolKind YAML coverage with -Wswitch (PR #225945)

[Andre Sun via cfe-commits]

and2049 wrote:

Buildkite is failing during checkout before any compilation or tests run with "fatal: couldn't find remote ref refs/pull/225945/head". I pushed a metadata amendment to trigger a fresh run, but it hit the same failure. 

https://github.com/llvm/llvm-project/pull/225945