[Bug libstdc++/101258] std ::is_integral_v is undocumented

[giecrilj at stegny dot 2a.pl via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101258

--- Comment #3 from Christopher Yeleighton <giecrilj at stegny dot 2a.pl> ---
It should at least be present on the API page.  The standard is not for
developers.