Remove Ambassador Host reduntant label filter test

Removing the `valid matching label filter expression` test in favour of just using `valid matching label filter expression for single host` as it is testing the same thing that a Ambassador Host with a valid label is matched.

Disscussed with alebedev87 in kubernetes-sigs#2633 (comment)

source/ambassador_host_test.go

@@ -364,42 +364,6 @@ func testAmbassadorSourceEndpoints(t *testing.T) {
 			},
 			expected: []*endpoint.Endpoint{},
 		},
-		{
-			title:            "valid matching label filter expression",
-			targetNamespace:  "",
-			// annotationFilter: "kubernetes.io/ingress.class in (external-ingress)",
-			labelSelector: labels.SelectorFromSet(labels.Set{"kubernetes.io/ingress.class": "external-ingress"}),
-			loadBalancer: fakeAmbassadorLoadBalancerService{
-				ips:       []string{"8.8.8.8"},
-				hostnames: []string{"lb.com"},
-				name:      "emissary",
-				namespace: "emissary-ingress",
-			},
-			ambassadorHostItems: []fakeAmbassadorHost{
-				{
-					name:      "fake1",
-					namespace: "testing1",
-					hostname:  "fake1.org",
-					annotations: map[string]string{
-						"external-dns.ambassador-service": "emissary-ingress/emissary",
-						"kubernetes.io/ingress.class":     "external-ingress",
-					},
-					labels: map[string]string{
-						"kubernetes.io/ingress.class": "external-ingress",
-					},
-				},
-			},
-			expected: []*endpoint.Endpoint{
-				{
-					DNSName: "fake1.org",
-					Targets: endpoint.Targets{"8.8.8.8"},
-				},
-				{
-					DNSName: "fake1.org",
-					Targets: endpoint.Targets{"lb.com"},
-				},
-			},
-		},
 		{
 			title:            "valid non-matching label filter expression",
 			targetNamespace:  "",