release-0.7: Bump golang to v1.21.8 and k8s dependencies to v1.29.2 and fix CVEs

[dgrisonnet]

Bump all the things on release-0.7 to prepare for a new patch release.

Scanning the binary in the docker image after the go update yielded:

➜  /tmp govulncheck -mode=binary metrics-server
Scanning your binary for known vulnerabilities...

=== Symbol Results ===

Vulnerability #1: GO-2024-2611
    Infinite loop in JSON unmarshaling in google.golang.org/protobuf
  More info: https://pkg.go.dev/vuln/GO-2024-2611
  Module: google.golang.org/protobuf
    Found in: google.golang.org/protobuf@v1.32.0
    Fixed in: google.golang.org/protobuf@v1.33.0
    Example traces found:
      #1: json.Decoder.Peek
      #2: json.Decoder.Read
      #3: protojson.Unmarshal
      #4: protojson.UnmarshalOptions.Unmarshal

Your code is affected by 1 vulnerability from 1 module.
This scan found no other vulnerabilities in packages you import or modules you
require.

So I udpated protobuf aswell.

[k8s-ci-robot]

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[k8s-ci-robot]

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[serathius]

/lgtm