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.

tests/integration/api_token_test.go

@@ -483,8 +483,7 @@ func runTestCase(t *testing.T, testCase *requiredScopeTestCase, user *user_model
 				} else if minRequiredLevel == auth_model.Write {
 					unauthorizedLevel = auth_model.Read
 				} else {
-					assert.Failf(t, "Invalid test case", "Unknown access token scope level: %v", minRequiredLevel)
-					return
+					assert.FailNow(t, "Invalid test case: Unknown access token scope level: %v", minRequiredLevel)
 				}
 			}