Update Sentry service SLOs to reflect our current goals for support

Summary

Currently, Sentry SLO alerts are not actionable and are consuming EOC time and effort with no tangible results/solutions. The SLO notifications should be removed from paging, removed all-together, or set to a level that will not be as noisy.

Reference issue for other work: https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/15372

Related Incident(s)

Originating issue(s): production#6883 (closed)

Desired Outcome/Acceptance Criteria

This issue is completed when the EOC is no longer getting SLO pages about un-actionable Sentry service problems.

Associated Services

Corrective Action Issue Checklist

• Link the incident(s) this corrective action arose out of
• Give context for what problem this corrective action is trying to prevent from re-occurring
• Assign a severity label (this is the highest sev of related incidents, defaults to 'severity::4')
• Assign a priority (this will default to 'priority::4')