Fix #123228: GPU subdivision setting can be adjusted on an unsupported device

GPU subdivision is only supported on OpenGL backend. Exclude this
property for metal backend then.

Pull Request: https://projects.blender.org/blender/blender/pulls/123313

scripts/startup/bl_ui/space_userpref.py

@@ -900,6 +900,12 @@ class USERPREF_PT_viewport_subdivision(ViewportPanel, CenterAlignMixIn, Panel):
     bl_label = "Subdivision"
     bl_options = {'DEFAULT_CLOSED'}
 
+    @classmethod
+    def poll(cls, context):
+        import gpu
+        backend = gpu.platform.backend_type_get()
+        return backend == "OPENGL"
+
     def draw_centered(self, context, layout):
         prefs = context.preferences
         system = prefs.system