build(deps): bump k8s.io/client-go from 0.18.6 to 0.18.8 (#4074)

Bumps [k8s.io/client-go](https://github.com/kubernetes/client-go) from 0.18.6 to 0.18.8.
- [Release notes](https://github.com/kubernetes/client-go/releases)
- [Changelog](https://github.com/kubernetes/client-go/blob/master/CHANGELOG.md)
- [Commits](https://github.com/kubernetes/client-go/compare/v0.18.6...v0.18.8)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

go.mod

@@ -39,6 +39,6 @@ require (
 	gopkg.in/DataDog/dd-trace-go.v1 v1.26.0
 	k8s.io/api v0.18.8
 	k8s.io/apimachinery v0.18.8
-	k8s.io/client-go v0.18.6
+	k8s.io/client-go v0.18.8
 	k8s.io/klog v1.0.0
 )