[clang] [llvm] [AArch64] Remove Automatic Enablement of FEAT_F32MM (PR #85203)

[via cfe-commits]

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

I was the one who originally decided that f32mm should be automatically enabled like this, and in hindsight I agree that that was the wrong decision. GCC never implemented this, so this is making us more compatible, not less.

https://github.com/llvm/llvm-project/pull/85203