Fix typo in Monitor stage page

Why is this change being made?

This change corrects a typo in the Monitor Stage description. The word "Instrymentation" was misspelled and has been corrected to "Instrumentation" in the list of groups that make up the Monitor Stage. This minor edit improves the accuracy and readability of the documentation, ensuring that users can find the correct information about the Analytics Instrumentation group.

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
  • Division: If the update affects your division, share the MR in your division 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

Commits

• Update file _index.md

---

added HandbookContent label

assigned to @dennis

marked the checklist item Provided a concise title for this [Merge Request (MR)][mr] as completed

marked the checklist item Added a description to this MR explaining the reasons for the proposed change, per [say why, not just what][say-why-not-just-what] as completed

enabled automatic add to merge train when checks pass

approved this merge request

started a merge train

merged

mentioned in commit 58fbeabc