[Bug web/109355] Add a text warning to old gcc online manual stating it is out of date

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109355

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
We could add server rules to insert a banner into the HTML on every page, but
it's not trivial.

You might be thinking of PR 65699.