Also remove useless comment in test-assembler-riscv64

Change-Id: I28451386449f15542b02383d8bf1aa9c4539469c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3669660
Auto-Submit: ji qiu <qiuji@iscas.ac.cn>
Reviewed-by: Yahan Lu <yahan@iscas.ac.cn>
Commit-Queue: Yahan Lu <yahan@iscas.ac.cn>
Cr-Commit-Position: refs/heads/main@{#80768}