*: bump Kubernetes dependencies to v1.21.0 (prometheus-operator#3969)

Signed-off-by: Simon Pasquier <spasquie@redhat.com>

go.mod

@@ -30,11 +30,11 @@ require (
 	google.golang.org/protobuf v1.26.0
 	gopkg.in/alecthomas/kingpin.v2 v2.2.6
 	gopkg.in/yaml.v2 v2.4.0
-	k8s.io/api v0.20.2
-	k8s.io/apiextensions-apiserver v0.20.1
-	k8s.io/apimachinery v0.20.5
+	k8s.io/api v0.21.0
+	k8s.io/apiextensions-apiserver v0.21.0
+	k8s.io/apimachinery v0.21.0
 	k8s.io/client-go v12.0.0+incompatible
-	k8s.io/component-base v0.20.5
+	k8s.io/component-base v0.21.0
 	k8s.io/klog v1.0.0
 	k8s.io/klog/v2 v2.8.0
 	k8s.io/utils v0.0.0-20210305010621-2afb4311ab10
@@ -45,7 +45,7 @@ replace (
 	github.com/prometheus-operator/prometheus-operator/pkg/client => ./pkg/client
 	// A replace directive is needed for k8s.io/client-go because Cortex (which
 	// is an indirect dependency through Thanos) has a requirement on v12.0.0.
-	k8s.io/client-go => k8s.io/client-go v0.20.1
+	k8s.io/client-go => k8s.io/client-go v0.21.0
 	k8s.io/klog => github.com/simonpasquier/klog-gokit v0.3.0
-	k8s.io/klog/v2 => github.com/simonpasquier/klog-gokit/v2 v2.0.1
+	k8s.io/klog/v2 => github.com/simonpasquier/klog-gokit/v2 v2.1.0
 )