Bump github.com/zalando/skipper from 0.18.38 to 0.21.7

Bumps [github.com/zalando/skipper](https://github.com/zalando/skipper) from 0.18.38 to 0.21.7.
- [Release notes](https://github.com/zalando/skipper/releases)
- [Commits](zalando/skipper@v0.18.38...v0.21.7)

---
updated-dependencies:
- dependency-name: github.com/zalando/skipper
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

go.mod

@@ -12,11 +12,11 @@ require (
 	github.com/prometheus/client_golang v1.18.0
 	github.com/sirupsen/logrus v1.9.3
 	github.com/stretchr/testify v1.8.4
-	github.com/zalando/skipper v0.18.38
+	github.com/zalando/skipper v0.21.7
 	gopkg.in/alecthomas/kingpin.v2 v2.2.6
-	k8s.io/api v0.24.17
-	k8s.io/apimachinery v0.24.17
-	k8s.io/client-go v0.24.17
+	k8s.io/api v0.26.2
+	k8s.io/apimachinery v0.26.2
+	k8s.io/client-go v0.26.2
 )
 
 require (
@@ -33,7 +33,7 @@ require (
 	github.com/dimfeld/httppath v0.0.0-20170720192232-ee938bf73598 // indirect
 	github.com/emicklei/go-restful/v3 v3.10.1 // indirect
 	github.com/evanphx/json-patch v4.12.0+incompatible // indirect
-	github.com/go-logr/logr v1.2.4 // indirect
+	github.com/go-logr/logr v1.4.1 // indirect
 	github.com/go-openapi/jsonpointer v0.19.5 // indirect
 	github.com/go-openapi/jsonreference v0.20.0 // indirect
 	github.com/go-openapi/swag v0.19.14 // indirect
@@ -61,19 +61,19 @@ require (
 	github.com/prometheus/common v0.45.0 // indirect
 	github.com/prometheus/procfs v0.12.0 // indirect
 	github.com/rcrowley/go-metrics v0.0.0-20201227073835-cf1acfcdf475 // indirect
-	github.com/redis/go-redis/v9 v9.2.1 // indirect
+	github.com/redis/go-redis/v9 v9.5.1 // indirect
 	github.com/tidwall/pretty v1.2.1 // indirect
 	go.uber.org/atomic v1.10.0 // indirect
 	go4.org/netipx v0.0.0-20230125063823-8449b0a6169f // indirect
-	golang.org/x/crypto v0.17.0 // indirect
-	golang.org/x/net v0.17.0 // indirect
-	golang.org/x/oauth2 v0.13.0 // indirect
-	golang.org/x/sys v0.15.0 // indirect
-	golang.org/x/term v0.15.0 // indirect
+	golang.org/x/crypto v0.19.0 // indirect
+	golang.org/x/net v0.21.0 // indirect
+	golang.org/x/oauth2 v0.17.0 // indirect
+	golang.org/x/sys v0.17.0 // indirect
+	golang.org/x/term v0.17.0 // indirect
 	golang.org/x/text v0.14.0 // indirect
-	golang.org/x/time v0.3.0 // indirect
-	google.golang.org/appengine v1.6.7 // indirect
-	google.golang.org/protobuf v1.31.0 // indirect
+	golang.org/x/time v0.5.0 // indirect
+	google.golang.org/appengine v1.6.8 // indirect
+	google.golang.org/protobuf v1.32.0 // indirect
 	gopkg.in/go-playground/assert.v1 v1.2.1 // indirect
 	gopkg.in/go-playground/validator.v9 v9.31.0 // indirect
 	gopkg.in/inf.v0 v0.9.1 // indirect
@@ -84,5 +84,5 @@ require (
 	k8s.io/utils v0.0.0-20230220204549-a5ecb0141aa5 // indirect
 	sigs.k8s.io/json v0.0.0-20220713155537-f223a00ba0e2 // indirect
 	sigs.k8s.io/structured-merge-diff/v4 v4.2.3 // indirect
-	sigs.k8s.io/yaml v1.3.0 // indirect
+	sigs.k8s.io/yaml v1.4.0 // indirect
 )