globals: interfere singleton-ness from the Singleton enum

src/ifs/workspace_manager/ext_workspace_manager_v1.rs

@@ -211,10 +211,6 @@ global_base!(
 );
 
 impl Global for ExtWorkspaceManagerV1Global {
-    fn singleton(&self) -> bool {
-        true
-    }
-
     fn version(&self) -> u32 {
         1
     }