Improve visibility of size limit enforcement

The info about the enforcement of the size limit on the Project API
was not obvious at first glance in the subheading linked from the
14.0 breaking-changes blog post. Make it VERY obvious.

doc/api/projects.md

@@ -313,7 +313,7 @@ When the user is authenticated and `simple` is not set this returns something li
 ```
 
 NOTE:
-The `tag_list` attribute has been deprecated 
+The `tag_list` attribute has been deprecated
 and is removed in API v5 in favor of the `topics` attribute.
 
 NOTE:
@@ -977,7 +977,7 @@ GET /projects/:id
 ```
 
 NOTE:
-The `tag_list` attribute has been deprecated 
+The `tag_list` attribute has been deprecated
 and is removed in API v5 in favor of the `topics` attribute.
 
 Users of [GitLab Premium or higher](https://about.gitlab.com/pricing/)
@@ -2046,7 +2046,8 @@ POST /projects/:id/restore
 ## Upload a file
 
 Uploads a file to the specified project to be used in an issue or merge request
-description, or a comment.
+description, or a comment. GitLab versions 14.0 and later
+[enforce](#max-attachment-size-enforcement) this limit.
 
 ```plaintext
 POST /projects/:id/uploads