Added info on how to patch a helm based install of GitLab

Why is this change being made?

We currently have the steps on how to patch an Omnibus install of GitLab, but we can't follow the same steps to patch a Kubernetes install of GitLab.

The MR contains a general summary on how to properly patch a Kubernetes based install GitLab.

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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  • The when to get approval handbook section explains the workflow in more detail
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  • If this is a change that directly impacts the majority of global team members, it should be a candidate for #company-fyi. Please work with internal communications and check the handbook for examples.

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