Align terminology and labels in prioritization table with agreed upon guidance for customer commitments

Why is this change being made?

Related to: https://gitlab.com/gitlab-com/Product/-/issues/3316

Per guidance in the product handbook,

It is important to note that the planning priority label does not constitute a promise for the issue to be delivered in any given milestone or timeframe.

This MR aligns terminology of the prioritization table to the handbook guidance by changing promised to customers to requested by customers

--> changed to Committed Priority to Customers per this Applied Suggestion.

Author Checklist

• Provided a concise title for the 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.
• Assign reviewers for this change to the correct DRI(s)
  • 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 in 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.
• 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.
  • 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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