Fix Gnus group name reference in gnus-mark-xrefs-as-read

* lisp/gnus/gnus-sum.el (gnus-mark-xrefs-as-read): There's already a
local binding for "group", don't need another "name". This was left
over from the obarray-to-hashtable change.
1 job for master in 56 minutes and 27 seconds (queued for 3 seconds)
Status Job ID Name Coverage
failed #2881


Name Stage Failure
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:959: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1