Add access note to Jira app self-managed doc

doc/integration/jira/connect-app.md

@@ -76,7 +76,7 @@ If the app requires additional permissions, [the update must first be manually a
 ## Install the GitLab.com for Jira Cloud app for self-managed instances **(FREE SELF)**
 
 If your GitLab instance is self-managed, you must follow some
-extra steps to install the GitLab.com for Jira Cloud app.
+extra steps to install the GitLab.com for Jira Cloud app, and your GitLab instance must be accessible by Jira.
 
 Each Jira Cloud application must be installed from a single location. Jira fetches
 a [manifest file](https://developer.atlassian.com/cloud/jira/platform/connect-app-descriptor/)