Upgrade kubectl to 1.19 in dev tooling.

[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:

Which issue(s) this PR fixes:

Work on #2129

Special notes for your reviewer:

[agones-bot]

Build Succeeded 👏

Build Id: 5814c7a6-92f4-4981-9b0e-51c31ef79dd7

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

• image: gcr.io/agones-images/agones-controller:1.16.0-7d5d414
• image: gcr.io/agones-images/agones-ping:1.16.0-7d5d414
• Linux C++ SDK (build): agonessdk-1.16.0-7d5d414-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.16.0-7d5d414.zip

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

• https://7d5d414-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/2147/head:pr_2147 && git checkout pr_2147
• helm install ./install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.16.0-7d5d414

[google-oss-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: markmandel, roberthbailey

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• OWNERS [markmandel,roberthbailey]

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