Fix #147926: Incorrect Icon used for Generic Collection

We have icons that represent specific individual collections. like
Icon_Outliner_Collection for a default (uncolored) collection, and
Icon_Collection_color_x for ones with colors. For "collections" as a
general thing though we have icon_group. Sometimes we confuse the two,
for example the list of tabs to show in Properties uses a different
icon than the actual category icon. This PR fixes the complaint by
using the correct icon for each of these purposes.

Pull Request: https://projects.blender.org/blender/blender/pulls/147942

scripts/startup/bl_ui/space_outliner.py

@@ -472,7 +472,7 @@ class OUTLINER_PT_filter(Panel):
         row.prop(space, "use_filter_view_layers", text="All View Layers")
 
         row = col.row()
-        row.label(icon='OUTLINER_COLLECTION')
+        row.label(icon='GROUP')
         row.prop(space, "use_filter_collection", text="Collections")
 
         row = col.row()

scripts/startup/bl_ui/space_properties.py

@@ -17,7 +17,7 @@ tab_list = [
     ("show_properties_view_layer", "View Layer", 'RENDERLAYERS'),
     ("show_properties_scene", "Scene", 'SCENE_DATA'),
     ("show_properties_world", "World", 'WORLD'),
-    ("show_properties_collection", "Collection", 'OUTLINER_COLLECTION'),
+    ("show_properties_collection", "Collection", 'GROUP'),
     ("show_properties_object", "Object", 'OBJECT_DATA'),
     ("show_properties_modifiers", "Modifiers", 'MODIFIER'),
     ("show_properties_effects", "Effects", 'SHADERFX'),