Fix T76778: Dopesheet "Show Errors" affects timeline

Since the timeline is a variation of the dopesheet, it also respects
some of the dopesheet settings.

The "Selected Only" setting is overridden from a scene property (since
rB4904eadc0f38) and the "Display Hidden" dopesheet setting seems to be
ignored.

This commit adds the remaining "Show Errors" setting to the menu,
allowing it to be updated from the timeline.

release/scripts/startup/bl_ui/space_time.py

@@ -142,6 +142,7 @@ class TIME_MT_view(Menu):
         layout.separator()
 
         layout.prop(scene, "show_keys_from_selected_only")
+        layout.prop(st.dopesheet, "show_only_errors")
 
         layout.separator()