[llvm] [RISCV] Remove experimental- prefix for smaia and ssaia. (PR #71172)

[Yeting Kuo via llvm-commits]

yetingk wrote:

> Wait, you may need to update `llvm/unittests/Support/RISCVISAInfoTest.cpp` too?

Sorry, I missed the file. I only test in llvm/test.

https://github.com/llvm/llvm-project/pull/71172