Bump k8s deps for 1.21.0 release

See also projectcontour/contour#3581

Signed-off-by: Sunjay Bhatia <sunjayb@vmware.com>

go.mod

@@ -4,19 +4,17 @@ go 1.15
 
 require (
 	github.com/docker/distribution v2.7.1+incompatible
-	github.com/go-logr/logr v0.3.0
-	github.com/go-logr/zapr v0.2.0 //indirect
+	github.com/go-logr/logr v0.4.0
 	github.com/onsi/ginkgo v1.14.1
 	github.com/onsi/gomega v1.10.2
 	github.com/opencontainers/go-digest v1.0.0 // indirect
 	github.com/projectcontour/contour v1.9.0
-	github.com/sclevine/agouti v3.0.0+incompatible // indirect
-	k8s.io/api v0.20.2
-	k8s.io/apiextensions-apiserver v0.20.1
-	k8s.io/apimachinery v0.20.2
-	k8s.io/client-go v0.20.2
-	k8s.io/utils v0.0.0-20201110183641-67b214c5f920
-	sigs.k8s.io/controller-runtime v0.8.0
+	k8s.io/api v0.21.0
+	k8s.io/apiextensions-apiserver v0.21.0
+	k8s.io/apimachinery v0.21.0
+	k8s.io/client-go v0.21.0
+	k8s.io/utils v0.0.0-20210305010621-2afb4311ab10
+	sigs.k8s.io/controller-runtime v0.8.2
 	sigs.k8s.io/controller-tools v0.4.1
 	sigs.k8s.io/gateway-api v0.2.0
 )