Fix add-on Preferences using the .blend file icon, not the Blender logo

Intention of the icon is to mark add-ons that are official/bundled.
Doesn't make much sense to use the .blend file icon for that. It's
arguable if the Blender logo should be used for this, but the file icon
is definitely the wrong choice.

release/scripts/startup/bl_ui/space_userpref.py

@@ -1808,7 +1808,7 @@ class USERPREF_PT_addons(AddOnPanel, Panel):
     bl_options = {'HIDE_HEADER'}
 
     _support_icon_mapping = {
-        'OFFICIAL': 'FILE_BLEND',
+        'OFFICIAL': 'BLENDER',
         'COMMUNITY': 'COMMUNITY',
         'TESTING': 'EXPERIMENTAL',
     }