RISC-V: Removed misleading comments in testcases

This patch removed the misleading comments in testcases since we
support fold min(int, poly) to constant by this patch
(https://gcc.gnu.org/pipermail/gcc-patches/2023-September/629651.html).
Thereby the csrr will not appear inside the assembly code, even if there
is no support for some VLS vector patterns.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/vls/div-1.c: Removed comments.
	* gcc.target/riscv/rvv/autovec/vls/shift-3.c: Ditto.