gh-106948: Update documentation nitpick_ignore for c:identifer domain (#107295)

gh-106948: Update documentation nitpick_ignore for c:identifer domain (#107295)

Update the nitpick_ignore of the documentation configuration to fix
Sphinx warnings about standard C types when declaring functions with
the "c:function" markups.

Copy standard C types declared in the "c:type" domain to the
"c:identifier" domain, since "c:function" markup looks for types in
the "c:identifier" domain.

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>