Consistently use @minus{} for negative arguments

Consistently use @minus{} for negative arguments

* doc/emacs/mark.texi (Marking Objects):
* doc/misc/gnus.texi (Selecting a Group):
* doc/emacs/programs.texi (Comment Commands):
* doc/emacs/killing.texi (Deletion):
* doc/emacs/display.texi (Recentering):
* doc/lispref/display.texi (Face Attributes):
* doc/lispref/searching.texi (String Search, Regexp Search):
Make the markup of "-N" use @minus{} uniformly.  (Bug#35885)