Clean up Gnus manual reference to XEmacs variables

* doc/misc/gnus.texi (XVarious): Remove section about XEmacs
variables that have been removed.
1 job for master in 65 minutes and 20 seconds (queued for 5 seconds)
Status Job ID Name Coverage
failed #2980


Name Stage Failure
test-all Test
Makefile:318: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/emacs/emacs/test'
make[2]: *** [check-doit] Error 1
make[1]: *** [check-expensive] Error 2
Makefile:293: recipe for target 'check-expensive' failed
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:959: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1