[llvm] [RISCV] Remove riscv-experimental-rv64-legal-i32. (PR #102509)

[Pengcheng Wang via llvm-commits]

https://github.com/wangpc-pp approved this pull request.

That would be a lot of clean-ups here.
LGTM if you think we won't keep developing this.

https://github.com/llvm/llvm-project/pull/102509