Add back preview headers for Pages APIs in GHAE (#22270)

Author: yoannchaudet

content/rest/overview/api-previews.md

@@ -190,7 +190,7 @@ You can now provide more information in GitHub for URLs that link to registered
 **Custom media types:** `corsair-preview`
 **Announced:** [2018-12-10](https://developer.github.com/changes/2018-12-10-content-attachments-api/)
 
-{% ifversion ghes < 3.3 %}
+{% ifversion ghae or ghes < 3.3 %}
 
 ## Enable and disable Pages