fix forkAPI test

Author: ben.durrant

packages/toolkit/src/listenerMiddleware/tests/fork.test.ts

@@ -367,7 +367,7 @@ describe('fork', () => {
         },
       })
 
-      store.dispatch(increment)
+      store.dispatch(increment())
 
       expect(await deferredResult).toBe(listenerCompleted)
     })