[RISCV][Clang] Drop the assembly tests for RVV intrinsics.

We had verified the correctness of all intrinsics in downstream, so
dropping the assembly tests to decrease the check-clang time.
It would remove 1/3 of the RUN lines.

https://reviews.llvm.org/D99151#2654154 mentions why we need to have
the ASM tests before.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D100617