Add the new gke-gcloud-auth-plugin binary to the build image

[roberthbailey]

What type of PR is this?

Uncomment only one /kind <> line, press enter to put that in a new line, and remove leading whitespace from that line:

/kind breaking
/kind bug
/kind cleanup
/kind documentation
/kind feature
/kind hotfix

What this PR does / Why we need it: Without this change, you can no longer fetch credentials for GKE clusters after running make shell, which also causes make gen-embedded-openapi to fail.

Which issue(s) this PR fixes:

Work on #2494

Special notes for your reviewer: See https://cloud.google.com/blog/products/containers-kubernetes/kubectl-auth-changes-in-gke

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pooneh-m, roberthbailey

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [pooneh-m,roberthbailey]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[agones-bot]

Build Failed 😱

Build Id: 60cebd37-ee68-4794-8440-8729d058acad

• Cloud Build view
• Cloud Build log download

To get permission to view the Cloud Build view, join the agones-discuss Google Group.

[roberthbailey]

Flake:

--- FAIL: TestGameServerRestartBeforeReadyCrash (207.29s)
    gameserver_test.go:354: 
        	Error Trace:	gameserver_test.go:354
        	Error:      	Received unexpected error:
        	            	timed out waiting for the condition
        	Test:       	TestGameServerRestartBeforeReadyCrash
FAIL

[agones-bot]

Build Succeeded 👏

Build Id: a71ff3b0-98c1-405f-b38d-0c09f18fb785

The following development artifacts have been built, and will exist for the next 30 days:

• image: gcr.io/agones-images/agones-controller:1.23.0-72110c4
• image: gcr.io/agones-images/agones-ping:1.23.0-72110c4
• Linux C++ SDK (build): agonessdk-1.23.0-72110c4-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.23.0-72110c4.zip

A preview of the website (the last 30 builds are retained):

• https://72110c4-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/2561/head:pr_2561 && git checkout pr_2561
• helm install ./install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.23.0-72110c4