Revert "[gnome-shell.modules] Work around problem of git with 'gtk+'"

This reverts commit b76fe12209.

We now have a workaround symlink server side for the git 1.7.2 handling
of '+', and also there's a patch in git upstream and in some distros, so
we don't need the workaround around in our moduleset anymore.

https://bugzilla.gnome.org/show_bug.cgi?id=626302

tools/build/gnome-shell.modules

@@ -85,7 +85,7 @@
   </autotools>
 
   <autotools id="gtk3">
-    <branch checkoutdir="gtk3" repo="git.gnome.org" module="gtk%2b"/>
+    <branch checkoutdir="gtk3" repo="git.gnome.org" module="gtk+"/>
     <dependencies>
       <dep package="glib"/>
       <dep package="pango"/>