Update sanitizer_coverage_allowlist_ignorelist.cpp to use POSIX-compliant regex (#176396)

As `\+` is a GNU extension, it is not supported by the system grep on
AIX. This change replaces `%[0-9]\+` with `%[0-9][0-9]*`, which is
POSIX-compliant and therefore compatible with AIX.

GitOrigin-RevId: 90895531ccd4fa6ad5d5062604d8f3dd34dcf741