fix(deps): update module sigs.k8s.io/controller-runtime to v0.21.0 (#367)

| datasource | package                        | from    | to      |
| ---------- | ------------------------------ | ------- | ------- |
| go         | sigs.k8s.io/controller-runtime | v0.20.4 | v0.21.0 |

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

go.mod

@@ -21,7 +21,7 @@ require (
 	k8s.io/apimachinery v0.33.1
 	k8s.io/client-go v0.33.1
 	k8s.io/utils v0.0.0-20250502105355-0f33e8f1c979
-	sigs.k8s.io/controller-runtime v0.20.4
+	sigs.k8s.io/controller-runtime v0.21.0
 	sigs.k8s.io/kustomize/api v0.19.0
 	sigs.k8s.io/kustomize/kyaml v0.19.0
 )

go.sum

@@ -310,8 +310,8 @@ k8s.io/utils v0.0.0-20250502105355-0f33e8f1c979 h1:jgJW5IePPXLGB8e/1wvd0Ich9QE97
 k8s.io/utils v0.0.0-20250502105355-0f33e8f1c979/go.mod h1:OLgZIPagt7ERELqWJFomSt595RzquPNLL48iOWgYOg0=
 sigs.k8s.io/apiserver-network-proxy/konnectivity-client v0.31.2 h1:jpcvIRr3GLoUoEKRkHKSmGjxb6lWwrBlJsXc+eUYQHM=
 sigs.k8s.io/apiserver-network-proxy/konnectivity-client v0.31.2/go.mod h1:Ve9uj1L+deCXFrPOk1LpFXqTg7LCFzFso6PA48q/XZw=
-sigs.k8s.io/controller-runtime v0.20.4 h1:X3c+Odnxz+iPTRobG4tp092+CvBU9UK0t/bRf+n0DGU=
-sigs.k8s.io/controller-runtime v0.20.4/go.mod h1:xg2XB0K5ShQzAgsoujxuKN4LNXR2LfwwHsPj7Iaw+XY=
+sigs.k8s.io/controller-runtime v0.21.0 h1:CYfjpEuicjUecRk+KAeyYh+ouUBn4llGyDYytIGcJS8=
+sigs.k8s.io/controller-runtime v0.21.0/go.mod h1:OSg14+F65eWqIu4DceX7k/+QRAbTTvxeQSNSOQpukWM=
 sigs.k8s.io/gateway-api v1.1.0 h1:DsLDXCi6jR+Xz8/xd0Z1PYl2Pn0TyaFMOPPZIj4inDM=
 sigs.k8s.io/gateway-api v1.1.0/go.mod h1:ZH4lHrL2sDi0FHZ9jjneb8kKnGzFWyrTya35sWUTrRs=
 sigs.k8s.io/json v0.0.0-20241014173422-cfa47c3a1cc8 h1:gBQPwqORJ8d8/YNZWEjoZs7npUVDpVXUUOFfW6CgAqE=