completion: add completions for git config commit

Add missing completions for git config:

* commit.cleanup
* commit.gpgSign
* commit.verbose
Signed-off-by: NRikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -2392,8 +2392,11 @@ _git_config ()
 		color.status.untracked
 		color.status.updated
 		color.ui
+		commit.cleanup
+		commit.gpgSign
 		commit.status
 		commit.template
+		commit.verbose
 		core.abbrev
 		core.askpass
 		core.attributesfile