Refactor: libcrmcommon: Drop pcmk__xc_same_position()
The logic is now in xml.c in a static function. It would be nice to keep
it in xml_comment.c for logical separation, but we're now checking
one-by-one so we can't keep track of the position in a loop.
Signed-off-by: Reid Wahl <nrwahl@protonmail.com>