Bump knative.dev/client from 0.23.1 to 0.26.0 (#291)

Bumps [knative.dev/client](https://github.com/knative/client) from 0.23.1 to 0.26.0.
- [Release notes](https://github.com/knative/client/releases)
- [Changelog](https://github.com/knative/client/blob/main/CHANGELOG.adoc)
- [Commits](knative/client@v0.23.1...v0.26.0)

---
updated-dependencies:
- dependency-name: knative.dev/client
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

go.mod

@@ -35,9 +35,9 @@ require (
  github.com/phayes/freeport v0.0.0-20180830031419-95f893ade6f2
  github.com/rcrowley/go-metrics v0.0.0-20201227073835-cf1acfcdf475
  github.com/rs/cors v1.7.0
- github.com/spf13/cobra v1.1.3
+ github.com/spf13/cobra v1.2.1
  github.com/spf13/pflag v1.0.5
- github.com/spf13/viper v1.8.0
+ github.com/spf13/viper v1.8.1
  github.com/tcnksm/go-httpstat v0.2.1-0.20191008022543-e866bb274419
  github.com/tidwall/gjson v1.8.0
  github.com/tomasen/realip v0.0.0-20180522021738-f0c99a92ddce
@@ -50,14 +50,13 @@ require (
  go.etcd.io/etcd/server/v3 v3.5.0
  go.uber.org/zap v1.19.0
  golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
- golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1
+ golang.org/x/sys v0.0.0-20210616094352-59db8d763f22
  gopkg.in/yaml.v2 v2.4.0
- k8s.io/api v0.20.7
- k8s.io/apimachinery v0.20.7
- k8s.io/cli-runtime v0.20.7 // indirect
- k8s.io/client-go v0.20.7
- knative.dev/client v0.23.1
- knative.dev/serving v0.23.1-0.20210614141420-380a090c2039
+ k8s.io/api v0.21.4
+ k8s.io/apimachinery v0.21.4
+ k8s.io/client-go v0.21.4
+ knative.dev/client v0.26.0
+ knative.dev/serving v0.26.0
 )
 
 replace github.com/go-openapi/spec => github.com/go-openapi/spec v0.19.3