vim: Disable gutentags when editing git-commits

Disable gutentags as it seems to regenerate the entire tags file when
editing git-commits, leading to a delay when exiting and a message from
git:
"Waiting for your editor to close the file..."

.config/vim/ftplugin/gitcommit.vim

@@ -3,3 +3,7 @@ setlocal colorcolumn=50,72
 setlocal textwidth=72
 " Spell checking always enabled
 setlocal spell spelllang=en
+
+" Disable gutentags as it seems to regenerate the entire tags file when editing
+" git-commits...
+let g:gutentags_enabled = 0