Replace assert.Fail with assert.FailNow (#27578)

assert.Fail() will continue to execute the code while assert.FailNow()
not. I thought those uses of assert.Fail() should exit immediately.
PS: perhaps it's a good idea to use
[require](https://pkg.go.dev/github.com/stretchr/testify/require)
somewhere because the assert package's default behavior does not exit
when an error occurs, which makes it difficult to find the root error
reason.

services/pull/check_test.go

@@ -54,7 +54,7 @@ func TestPullRequest_AddToTaskQueue(t *testing.T) {
 	case id := <-idChan:
 		assert.EqualValues(t, pr.ID, id)
 	case <-time.After(time.Second):
-		assert.Fail(t, "Timeout: nothing was added to pullRequestQueue")
+		assert.FailNow(t, "Timeout: nothing was added to pullRequestQueue")
 	}
 
 	has, err = prPatchCheckerQueue.Has(strconv.FormatInt(pr.ID, 10))