Delete Katacoda link(404) because Katacoda is closed

[govargo]

What type of PR is this?

/kind bug
/kind documentation

What this PR does / Why we need it:

When I ran make test, the htmltest failed with the following error.

Html Test: Attempt 1
htmltest started at 03:06:16 on /tmp/website
========================================================================
site/docs/prerequisite-knowledge/index.html
  Non-OK status: 404 --- site/docs/prerequisite-knowledge/index.html --> https://www.katacoda.com/courses/docker
  Non-OK status: 404 --- site/docs/prerequisite-knowledge/index.html --> https://www.katacoda.com/courses/kubernetes

Katacoda is now closed, so the link was 404.
In this PR, delete katacoda links.

Which issue(s) this PR fixes:

None

Special notes for your reviewer:

None

[agones-bot]

Build Failed 😱

Build Id: 73eaff6a-71aa-40d0-85c7-4a80821531eb

• Cloud Build view
• Cloud Build log download

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[markmandel]

It's so sad these resources are gone 😭

[markmandel]

Ah this ol' chestnut:

--- FAIL: TestFleetRollingUpdate (0.00s)
    --- FAIL: TestFleetRollingUpdate/Use_fleet_Patch_true_25%_cycle_true (98.40s)
        fleet_test.go:413: 
            	Error Trace:	fleet_test.go:413
            	Error:      	Condition never satisfied
            	Test:       	TestFleetRollingUpdate/Use_fleet_Patch_true_25%_cycle_true
FAIL

(e2e-stable)

• Flaky Test: TestFleetRollingUpdate/Use_fleet_Patch_true_25%_cycle_true #2522

[agones-bot]

Build Succeeded 👏

Build Id: f8708083-d42f-4a42-aab3-ba778d91acbe

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

• image: gcr.io/agones-images/agones-controller:1.24.0-52d2f89-amd64
• image: gcr.io/agones-images/agones-controller:1.24.0-52d2f89-arm64
• image: gcr.io/agones-images/agones-ping:1.24.0-52d2f89-amd64
• image: gcr.io/agones-images/agones-ping:1.24.0-52d2f89-arm64
• Linux C++ SDK (build): agonessdk-1.24.0-52d2f89-arm64-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.24.0-52d2f89-arm64.zip

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

• https://52d2f89-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/2640/head:pr_2640 && git checkout pr_2640
• helm install agones ./install/helm/agones --namespace agones-system --set agones.image.tag=1.24.0-52d2f89-amd64

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

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

The full list of commands accepted by this bot can be found here.

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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: e2152650-9e37-4e1d-807d-873ab26c34f7

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

• image: gcr.io/agones-images/agones-controller:1.24.0-f7bb172-amd64
• image: gcr.io/agones-images/agones-controller:1.24.0-f7bb172-arm64
• image: gcr.io/agones-images/agones-ping:1.24.0-f7bb172-amd64
• image: gcr.io/agones-images/agones-ping:1.24.0-f7bb172-arm64
• Linux C++ SDK (build): agonessdk-1.24.0-f7bb172-arm64-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.24.0-f7bb172-arm64.zip

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

• https://f7bb172-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/2640/head:pr_2640 && git checkout pr_2640
• helm install agones ./install/helm/agones --namespace agones-system --set agones.image.tag=1.24.0-f7bb172-amd64