Note that that's the same redirect it had been doing for a long time (except for a bit earlier today).
I'm not sure what happened, since the relevant file hasn't been committed to in a while: https://web.cvs.savannah.gnu.org/viewvc/www/www/licenses/.sy...
Probably was just a mistake, and has now been fixed, as the link structure on the page now points to https://www.gnu.org/licenses/gpl-3.0.html (note the 3.0 addition).
The original link submitted here (https://www.gnu.org/licenses/gpl.html) also forwards to that URL now.