doc(Provision): Extend error budget exception

Why is this change being made?

Fulfillment:Provision is still over the error budget and we will be until the issues below are closed.

We've seen improvements from resolving the original error budget issue, but after the change landed we discovered three additional issues that are either scheduled, or we are currently looking into. Provision will still be over the error budget until the issues below are closed:

1. gitlab-org/customers-gitlab-com#4884 (closed)
2. gitlab-org/customers-gitlab-com#4876 (closed)
3. gitlab-org/customers-gitlab-com#4875 (closed)

More information here: gitlab-org/error-budget-reports#15 (closed)

Author Checklist

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• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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• [-] If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR
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