test: gatewayclasss resources can be normally deleted after the test is completed

[ronething]

In the current test process, there may be a situation where the gatewayclass is not deleted normally. We need to consider how to delete normally.

ref:

api7-ingress-controller/test/e2e/crds/v1alpha1/gatewayproxy.go

Lines 143 to 145 in 1d99fad

	By("create GatewayClass")
	gatewayClassName := fmt.Sprintf("apisix-%d", time.Now().Unix())
	err = s.CreateResourceFromString(fmt.Sprintf(gatewayClassSpec, gatewayClassName, s.GetControllerName()))