[clang] [llvm] Remove experimental from Vector Crypto extensions (PR #69000)

[Brandon Wu via cfe-commits]

4vtomat wrote:

Since it's possible that **ISA spec** and **intrinsics spec** are not synchronized, so the updates add an dummy extension called **zexperimental**, once `-menable-experimental-extensions` is specified, the feature `zexperimental` is automatically added.
If specifying `let RequiredFeatures = ["Zexperimental"] ` is added in `.td` file, it will check if `zexperimental` exists, if not, the corresponding intrinsics would not be added, hence causing an **intrinsics undeclared** error.

https://github.com/llvm/llvm-project/pull/69000