[LyX/master] Fix gcc 13 compilation.

[José Matos]

On Sun, 2024-11-10 at 16:51 +0100, Scott Kostyshak wrote:
> I did not actually try -std=c++14 or something like that; maybe it
> would have worked.

In the particular case of the #include directives I would be really
surprised if this changed anything. All this work, usually, comes from
the reorganization of the standard library header files and thus should
be independent of the standard used.
-- 
José Abílio