tools/rv: Correct the grammatical errors in the comments

The word "trace" begins with a consonant sound,
so "a" should be used instead of "an".

Link: https://lore.kernel.org/20240903003019.8969-1-bajing@cmss.chinamobile.com


Signed-off-by: Ba Jing <bajing@cmss.chinamobile.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>