[RISCV][MC] Mark Zawrs extension as non-experimental

[RISCV][MC] Mark Zawrs extension as non-experimental

Support for the unratified 1.0-rc3 specification was introduced in
D133443. The specification has since been ratified (in November 2022
according to the recently ratified extensions list
<https://wiki.riscv.org/display/HOME/Recently+Ratified+Extensions>.

A review of the diff
<https://github.com/riscv/riscv-zawrs/compare/V1.0-rc3...main> of the
1.0-rc3 spec vs the current/ratified document shows no changes to the
instruction encoding or naming. At one point, a note was added
<https://github.com/riscv/riscv-zawrs/commit/e84f42406a7c88eb92452515b2035144a7023a51>
indicating Zawrs depends on the Zalrsc extension (not officially
specified, but I believe to be just the LR/SC instructions from the A
extension). The final text ended up as "The instructions in the Zawrs
extension are only useful in conjunction with the LR instructions, which
are provided by the A extension, and which we also expect to be provided
by a narrower Zalrsc extension in the future." I think it's consistent
with this phrasing to not require the A extension for Zawrs, which
matches what was implemented.

No intrinsics are implemented for Zawrs currently, meaning we don't need
to additionally review whether those intrinsics can be considered
finalised and ready for exposure to end users.

Differential Revision: https://reviews.llvm.org/D143507