[Bug c/99291] maybe_warn_pass_by_reference uses outdated format string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 #4 from Roland Illig <roland.illig at gmx dot de> ---
and another one, this time in aarch64.c:
> error ("%<%s%> must be by itself for %<-mharden-sls=%>", str);

This should be %qs as well.