Load test: Fix example yaml config

[aLekSer]

Change link to gcr.io/agones-images.

What type of PR is this?

Uncomment only one /kind <> line, hit 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:

Closes #

Special notes for your reviewer:

[agones-bot]

Build Succeeded 👏

Build Id: 7bbeb601-865f-48d0-829f-7d916826cb55

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

• image: gcr.io/agones-images/agones-controller:1.7.0-5632286
• image: gcr.io/agones-images/agones-sdk:1.7.0-5632286
• image: gcr.io/agones-images/agones-ping:1.7.0-5632286
• Linux C++ SDK (build): agonessdk-1.7.0-5632286-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.7.0-5632286.zip

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

• https://5632286-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/1634/head:pr_1634 && git checkout pr_1634
• helm install ./install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.7.0-5632286

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: akremsa, aLekSer, roberthbailey

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