test: add delay for flaky focus test (vercel#1762)

Author: huozhi

test/use-swr-focus.test.tsx

@@ -195,7 +195,11 @@ describe('useSWR - focus', () => {
     await focusWindow()
     // wait for throttle intervals
     await act(() => sleep(150))
-    await screen.findByText('data: 4')
+    // trigger revalidation
+    await focusWindow()
+    await waitForNextTick()
+    await act(() => sleep(100))
+    await screen.findByText('data: 5')
   })
 
   it('should revalidate on focus even with custom cache', async () => {