Simplify and de-lint GCE Windows kube-up docs.

[jeremyje]

What type of PR is this?

/kind documentation

What this PR does / why we need it:
Replaces instructions to patch in a forked commit with the proper build instructions. Resolve all markdownlint issues.

Which issue(s) this PR fixes:
N/A

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

Hi @jeremyje. Thanks for your PR.

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[yliaog]

/ok-to-test

[yliaog]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jeremyje, yliaog

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• cluster/gce/windows/OWNERS [yliaog]

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[fejta-bot]

/retest
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