Remove 'special' fragment from semantic versioning

Removed the 'special' fragment from OpenProject's semantic versioning, which was not in use. This change is ignorable unless relied upon in plugins.

Author: oliverguenther

docs/release-notes/17-0-0/README.md

@@ -22,6 +22,13 @@ In these Release Notes, we will give an overview of important feature changes. A
 
 <!-- Remove this section if empty, add to it in pull requests linking to tickets and provide information -->
 
+### Removal of special semver
+
+We removed the `special` fragment of the semantic version of OpenProject. This has not been in use.
+Unless you are relying on this value in one of your plugins, you can ignore this change.
+
+Reference: \[[#67036](https://community.openproject.org/wp/67036)\]
+
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 ## Bug fixes and changes