Stale wiki info about CompileFarm registration

[Yuri Gribov]

Hi all,

It seems that info at
https://gcc.gnu.org/wiki/CompileFarm#How_to_Get_Involved.3F is
out-dated: Laurent's mail is not responsive and one's supposed to use
application form at https://cfarm.tetaneutral.net/users/new/ (which
provides all the necessary guidance).

Could someone update the wiki? (I could do it myself but don't have
write access)

-Yury