Correct role required to view email address

The service desk internal email address appears to only be
available to maintainer roles or higher, not to every project
member (such as those with developer, or reporter roles
acting as support agents to the service desk feature)

doc/user/project/service_desk.md

@@ -86,9 +86,10 @@ To improve your project's security, we recommend the following:
 - [Enable Akismet](../../integration/akismet.md) on your GitLab instance to add spam checking to this service.
   Unblocked email spam can result in many spam issues being created.
 
-The unique internal email address is visible to all project members in your GitLab instance. 
-However, when using an email alias externally, an end user (issue creator) cannot see the internal
-email address displayed in the information note.
+The unique internal email address is visible to project members with Maintainer (or higher)
+[permission level](../permissions.md)
+in your GitLab instance. However, when using an email alias externally, an end user
+(issue creator) cannot see the internal email address displayed in the information note.
 
 ### Using customized email templates