Bug 1256988 - Remove duplicate gfx.content.azure.backends settings in all.js. r=chmanchester

They are useless because they replicate what is already set in the #else
case above them.

modules/libpref/init/all.js

@@ -723,13 +723,6 @@ pref("gfx.content.azure.backends", "cairo");
 #endif
 #endif
 
-#ifdef MOZ_WIDGET_GTK2
-pref("gfx.content.azure.backends", "cairo");
-#endif
-#ifdef ANDROID
-pref("gfx.content.azure.backends", "cairo");
-#endif
-
 pref("gfx.work-around-driver-bugs", true);
 pref("gfx.prefer-mesa-llvmpipe", false);