RISC-V: Adjust test case due to allow vwcvt.x[u].f.v overlap

Remove the xfail due to overlap changes.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/pr112431-13-0.c: Remove xfail.

Signed-off-by: Pan Li <pan2.li@intel.com>