[Bug libstdc++/99612] Remove "#pragma GCC system_header" from atomic file to warn on incorrect memory order

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99612

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'd prefer if the compiler just got it right. This seems like a warning that
should fire even in system headers. Or it should track that the value is a
function parameter and came from a non-system header and so the diagnostic
location should not consider the point of use.