[llvm] [ValueTypes] Remove MVT::MAX_ALLOWED_VALUETYPE. NFC (PR #93654)

[NAKAMURA Takumi via llvm-commits]

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

Thanks. Reasonable.
Could you wait for one more opinions?

> I can make this a separate change if desired.

I prefer it may be split in advance. It is a good cleanup.

https://github.com/llvm/llvm-project/pull/93654