(DOCSP-45740): Fix permissions for manage system alerts page (#607)

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- [DOCSP-45740](https://jira.mongodb.org/browse/DOCSP-45740)
-
[STAGING](https://deploy-preview-607--10gen-docs-ops-manager.netlify.app/core/system-alerts/)

### Self-Review Checklist

- [ ]
[Define](https://wiki.corp.mongodb.com/display/DE/Taxonomy+tagging+instructions)
taxonomy
[values](https://wiki.corp.mongodb.com/display/DE/Docs+Taxonomy) at top
of page.
- [ ] Add genre facets (tutorial or reference), as in this [example
PR](10gen/cloud-docs#5042).
- [ ] Add programmingLanguage (if necessary).
- [ ] Add meta keywords (if necessary).
- [x] Resolve any new warnings or errors in the build.
- [x] Proofread for spelling and grammatical errors.
- [x] Check staging for rendering issues.
- [x] Confirm links are working.

Author: davidhou17

source/core/system-alerts.txt

@@ -34,9 +34,7 @@ Disabled system alerts are grayed out.
 
 If you have the
 ``Global Owner``
-or
-``Global Monitoring Admin``
-roles, you can
+role, you can
 :ref:`modify notification settings <edit-system-alert-notification>`
 or :ref:`disable <disable-system-alert>` a system alert.