Docs: Fix rest GetPlayerCount description

[Reousa]

What type of PR is this?

/kind documentation

What this PR does / Why we need it:

Fixes the REST docs

Which issue(s) this PR fixes:
Closes #1810

Special notes for your reviewer:

I assumed that this behavior is also true for this entry:

This is always accurate from what has been set through this SDK, even if the value has yet to be updated on the GameServer status resource.

[agones-bot]

Build Failed 😱

Build Id: 75c431eb-8531-4792-afbe-1fd1b25c738b

• Cloud Build view
• Cloud Build log download

To get permission to view the Cloud Build view, join the agones-discuss Google Group.

[aLekSer]

It could be the case that we need to clean up E2E test cluster which could have dangling Fleets, as I saw it from my recent PRs updates and CI results.

[aLekSer]

Thanks for noticing this missing section.

[agones-bot]

Build Failed 😱

Build Id: 228b955a-53e7-4486-b8b5-8103f0950a4a

• Cloud Build view
• Cloud Build log download

To get permission to view the Cloud Build view, join the agones-discuss Google Group.

[aLekSer]

I expect that CI would be fixed after #1808 .

[Reousa]

Do tag me if a rebase is needed 👍

[agones-bot]

Build Failed 😱

Build Id: 543555a3-6e75-48cc-8925-07aae8a35129

• Cloud Build view
• Cloud Build log download

To get permission to view the Cloud Build view, join the agones-discuss Google Group.

[markmandel]

Good catch!

[google-oss-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aLekSer, markmandel, Reousa

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 [aLekSer,markmandel]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[agones-bot]

Build Succeeded 👏

Build Id: 31e1e9c5-2008-4b22-80ba-4f1d303125f1

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

• image: gcr.io/agones-images/agones-controller:1.9.0-9ae74ed
• image: gcr.io/agones-images/agones-sdk:1.9.0-9ae74ed
• image: gcr.io/agones-images/agones-ping:1.9.0-9ae74ed
• Linux C++ SDK (build): agonessdk-1.9.0-9ae74ed-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.9.0-9ae74ed.zip

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

• https://9ae74ed-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/1811/head:pr_1811 && git checkout pr_1811
• helm install ./install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.9.0-9ae74ed