Remove redundants "See" before @xref or @pxref (Bug#35793)

* doc/misc/gnus.texi (Group Parameters): Remove redundant "See" before
cross reference, add comma after it.
1 job for master in 74 minutes and 42 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #1901
test-all

01:14:42

 
Name Stage Failure
failed
test-all Test
make[2]: *** [check-doit] Error 1
Makefile:318: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:293: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:957: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1