(DOCSP-45740): Fix permissions for manage system alerts page-v6.0-backport (607) (#610)

# Backport

This will backport the following commits from `master` to `v6.0`:
- [(DOCSP-45740): Fix permissions for manage system alerts page
(#607)](10gen/docs-ops-manager#607)

<!--- Backport version: 9.6.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sorenlouv/backport)

Author: davidhou17

source/core/system-alerts.txt

@@ -30,9 +30,7 @@ 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.