Add step for trial exclusions acknowledgment

Why is this change being made?

💡 Provide a detailed answer to the question on why this change is being proposed, in accordance with our value of Transparency.

We discussed this topic in Slack, in the wake of a customer receiving an emergency trial license without knowing about its limitations:

I noticed that the Trial Subscription - Exclusions Sign Off Zendesk macro isn't mentioned in this workflow, which appears to be an oversight.

This MR also updates the instructions for handling a self-managed weekend license emergency, directing the user to the appropriate workflow instead of CustomersDot mechanizer page. Unlike the CustomersDot mechanizer page, the Weekend Emergencies - License Request page provides step-by-step instructions for self-managed license emergencies that happen over the weekend.

Related to !902 (merged)

Author and Reviewer Checklist

Please verify the check list and ensure to tick them off before the MR is merged.

• 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
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added, and the content is SAFE
• Assign reviewers for this MR to the correct Directly Responsible Individual/s (DRI)
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies
  • The when to get approval handbook section explains the workflow in more detail
• For transparency, share this MR with the audience that will be impacted.
  • Team: For changes that affect your direct team, share in your group Slack channel
  • Department: If the update affects your department, share the MR in your department Slack channel
  • Company: If the update affects all (or the majority of) GitLab team members, post an update in #whats-happening-at-gitlab linking to this MR
    • For high-priority company-wide announcements work with the internal communications team to post the update in #company-fyi and align on a plan to circulate in additional channels like the "While You Were Iterating" Newsletter

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