[llvm] [Docs] Fix link in LoopTerminology (NFC) (PR #131138)

[Benjamin Maxwell via llvm-commits]

https://github.com/MacDue approved this pull request.

LGTM, the `#id<number>` anchors are not stable (they change whenever a new header is added or moved). 

https://github.com/llvm/llvm-project/pull/131138