[Bug libstdc++/84671] [6/7/8 Regression] Chrono literals don't accept apostrophe as separator

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84671

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Presumably started with my commit r210513