Add docs on ignoring error

What does this MR do?

This adds docs for ignoring a Sentry error via the GitLab UI.

Related issues

#39665 (closed)

Author's checklist

• Follow the Documentation Guidelines and Style Guide.
• If applicable, update the permissions table.
• Link docs to and from the higher-level index page, plus other related docs where helpful.
• Apply the documentation label.

Review checklist

All reviewers can help ensure accuracy, clarity, completeness, and adherence to the Documentation Guidelines and Style Guide.

1. Primary Reviewer

• Review by a code reviewer or other selected colleague to confirm accuracy, clarity, and completeness. This can be skipped for minor fixes without substantive content changes.

2. Technical Writer

• Optional: Technical writer review. If not requested for this MR, must be scheduled post-merge. To request for this MR, assign the writer listed for the applicable DevOps stage.

3. Maintainer

1. Review by assigned maintainer, who can always request/require the above reviews. Maintainer's review can occur before or after a technical writer review.
2. Ensure a release milestone is set.
3. If there has not been a technical writer review, create an issue for one using the Doc Review template.

/label documentation

doc/user/project/operations/error_tracking.md

@@ -62,3 +62,15 @@ If the error has not been linked to an existing GitLab issue, a 'Create Issue' b
 If a link does exist, it will be shown in the details and the 'Create Issue' button will be hidden:
 
 ![Error Details with Issue Link](img/error_details_with_issue_v12_6.png)
+
+## Taking Action on errors
+
+You can take action on Sentry Errors from within the GitLab UI.
+
+### Ignoring errors
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/39665) in GitLab 12.7.
+
+From within the [Error Details](#error-details) page you can ignore a Sentry error by simply clicking the **Ignore** button near the top of the page.
+
+Ignoring an error will prevent it from appearing in the [Error Tracking List](#error-tracking-list), and will silence notifications that were set up within Sentry.