Drop deprecated dependency on moblin-icon-theme

In commit ef73e06 a .gktrc-2.0 workaround for a firefox
issue was added, and was removed via commit b008773 later
on, but the dependency on moblin-icon-theme was forgotten to be
removed.

Given that moblin-icon-theme was removed from Debian (see
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=979342),
remove this broken dependency also here.

debian/control

@@ -12,7 +12,7 @@ Bugs: mailto:bugs@grml.org
 
 Package: grml-desktop
 Architecture: all
-Depends: grml-scripts (>= 1.1.18), moblin-icon-theme, ${misc:Depends}
+Depends: grml-scripts (>= 1.1.18), ${misc:Depends}
 Recommends: fluxbox
 Description: configuration files for the X desktop at grml
  This package provides several configuration files for