Documentation: Allocated GameServer Overflow

[markmandel]

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:

Added documentation to the "Fleet Update" section on how notifications can occur for Fleet updates and related operations.

Which issue(s) this PR fixes:

Closes #2682

Special notes for your reviewer:

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

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

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 [markmandel]

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[google-oss-prow]

New changes are detected. LGTM label has been removed.

[agones-bot]

Build Succeeded 👏

Build Id: f19303c2-73ab-456a-9576-61e495611cde

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

• image: us-docker.pkg.dev/agones-images/ci/agones-controller:1.32.0-9fb52d1-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.32.0-9fb52d1-linux-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.32.0-9fb52d1-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.32.0-9fb52d1-amd64
• Linux C++ SDK (build): agonessdk-1.32.0-9fb52d1-amd64-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.32.0-9fb52d1-amd64.zip

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

• https://9fb52d1-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/3131/head:pr_3131 && git checkout pr_3131
• helm install agones ./install/helm/agones --namespace agones-system --agones.image.release=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.32.0-9fb52d1-amd64