[clang] [llvm] [RISCV] Remove experimental from Vector Crypto extensions (PR #74213)

[Eric Biggers via cfe-commits]

ebiggers wrote:

Updated to add my Co-authored-by, as the original author is `Brandon Wu <brandon.wu at sifive.com>`.

Someone who has permission to do so will need to approve the GitHub Actions workflow, and merge the commit once everything is ready.

https://github.com/llvm/llvm-project/pull/74213