fleetautoscaler.md references metadata incorrectly

[KAllan357]

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
/kind release

What this PR does / Why we need it:

I started to write my own Webhook Autoscaler using the documentation as a reference and never saw a metadata key in my scaling requests from Agones. I started researching the codebase and read through #3957 and the associated issues. I think this error in documentation slipped through during the code review and it was not updated to what actually shipped in that PR.

This change updates the documentation to match the struct again.

Which issue(s) this PR fixes:

Closes #

Special notes for your reviewer:

[markmandel]

/gcbrun

[agones-bot]

Build Failed 😭

Build Id: 23294625-e612-430d-bb7c-1f6d4a4e656a

Status: FAILURE

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[markmandel]

Flake:

    examples_test.go:83: 
        	Error Trace:	/go/src/agones.dev/agones/test/e2e/examples_test.go:83
        	Error:      	Received unexpected error:
        	            	waiting for {supertuxkart [{default  Dynamic <nil> 8080 0 UDP}] {false 60 0 30}  { 0 0} {{      0 0001-01-01 00:00:00 +0000 UTC <nil> <nil> map[] map[] [] [] []} {[] [] [{supertuxkart us-docker.pkg.dev/agones-images/examples/supertuxkart-example:0.18 [] []  [] [] [{ENABLE_PLAYER_TRACKING false nil}] {map[] map[] []} [] <nil> [] [] nil nil nil nil    nil false false false}] []  <nil> <nil>  map[]   <nil>  false false false <nil> nil []   nil  [] []  <nil> nil [] <nil> <nil> <nil> map[] [] <nil> nil <nil> [] [] nil}} <nil> map[] map[] <nil>} GameServer instance readiness timed out (): waiting for GameServer 1752211393/supertuxkart-bjxwp to be Ready: GameServer reached terminal state Unhealthy
        	Test:       	TestSuperTuxKartGameServerReady

Weird.

[markmandel]

/gcbrun

[agones-bot]

Build Succeeded 🥳

Build Id: 21a4dcf5-d417-45a3-a134-35657b2729e4

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:1.51.0-dev-d73d389
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.51.0-dev-d73d389
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.51.0-dev-d73d389-linux
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.51.0-dev-d73d389
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.51.0-dev-d73d389
• Linux C++ SDK (build): agonessdk-1.51.0-dev-d73d389-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.51.0-dev-d73d389.zip

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

• https://d73d389-dot-preview-dot-agones-images.appspot.com/

To install this version:

git fetch https://github.com/googleforgames/agones.git pull/4217/head:pr_4217 && git checkout pr_4217
helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.51.0-dev-d73d389

[markmandel]

Good catch! Thanks!

[markmandel]

/gcbrun

[agones-bot]

Build Succeeded 🥳

Build Id: ba0558ab-a4bf-4860-a697-6a70d627c215

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:1.51.0-dev-3e991a6
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.51.0-dev-3e991a6
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.51.0-dev-3e991a6-linux
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.51.0-dev-3e991a6
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.51.0-dev-3e991a6
• Linux C++ SDK (build): agonessdk-1.51.0-dev-3e991a6-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.51.0-dev-3e991a6.zip

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

• https://3e991a6-dot-preview-dot-agones-images.appspot.com/

To install this version:

git fetch https://github.com/googleforgames/agones.git pull/4217/head:pr_4217 && git checkout pr_4217
helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.51.0-dev-3e991a6