Asset Browser: Hide Import Types menu for "Current File" asset library

This menu doesn't have an effect on the importing while in the "Current File"
asset library. This can be quite confusing.

However, just hiding the menu may be a temporary solution. Decision
actually to instead show a different menu, that allows choosing between
duplicating and reusing data on drop. This is being reviewed here
https://developer.blender.org/D12879.
Meanwhile (or in case we end up rejecting that), this change should
avoid some confusion.

Differential Revision: https://developer.blender.org/D12752

release/scripts/startup/bl_ui/space_filebrowser.py

@@ -38,7 +38,8 @@ class FILEBROWSER_HT_header(Header):
 
         layout.separator_spacer()
 
-        layout.prop(params, "import_type", text="")
+        if params.asset_library_ref != 'LOCAL':
+            layout.prop(params, "import_type", text="")
 
         layout.separator_spacer()