Fix ACTION argument of 'display-buffer' call in gud.el

* lisp/progmodes/gud.el (gud-common-init): The ACTION argument of
'display-buffer' should be a list of list of functions.  (Bug#41888)
1 job for emacs-27 in 67 minutes and 7 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #6496
test-all

01:07:07