Add a missing word to clarify our policy for when to upgrade Kubernetes versions

[roberthbailey]

What type of PR is this?

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/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:

Closes #

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[agones-bot]

Build Succeeded 👏

Build Id: c95b2b52-5db9-4ef8-8cb8-9d88ce8d4dc6

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

• image: gcr.io/agones-images/agones-controller:1.17.0-d9a1ebc
• image: gcr.io/agones-images/agones-ping:1.17.0-d9a1ebc
• Linux C++ SDK (build): agonessdk-1.17.0-d9a1ebc-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.17.0-d9a1ebc.zip

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

• https://d9a1ebc-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/2212/head:pr_2212 && git checkout pr_2212
• helm install ./install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.17.0-d9a1ebc

[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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