[llvm] [RISCV] Remove`riscv.segN.load/store` in favor of their mask variants (PR #137045)

[Min-Yih Hsu via llvm-commits]

mshockwave wrote:

> I think we should not call it "deprecate" if you're deleting them. Most of the time when we say we're deprecating something in LLVM, it's still usable for a time with maybe a warning.

Agree. The title is updated now.

https://github.com/llvm/llvm-project/pull/137045