[Bug c/99291] maybe_warn_pass_by_reference uses outdated format string

[roland.illig at gmx dot de via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99291

--- Comment #2 from Roland Illig <roland.illig at gmx dot de> ---
Plus, there is a typo:
> %<-march=%s%>: Extension `%s' appear more than one time.

Either it must be 'Extensions' or 'appears'.