changelog: add release PR URL

Author: MichaIng

CHANGELOG.txt

@@ -29,7 +29,7 @@ Bug fixes:
 - DietPi-Software | Home Assistant: Worked around an issue where the installation and service start failed due to a missing upper dependency declaration. The issue has been solved at Home Assistant for their upcoming release, which will make our workaround obsolete.
 - DietPi-Software | BirdNET-Go: The latest (pre-)release will now be detected and installed instead of a hardcoded version, which solves an upstream bug where reviewing bird detections did not work. Many thanks to @Sonnenfleck and @oturn for reporting the issue and testing newer versions, as well as @JappeHallunken for implementing the dynamic release download: https://github.com/MichaIng/DietPi/issues/7861, https://github.com/MichaIng/DietPi/issues/7861
 
-As always, many smaller code performance and stability improvements, visual and spelling fixes have been done, too much to list all of them here. Check out all code changes of this release on GitHub: https://github.com/MichaIng/DietPi/pull/ADDME
+As always, many smaller code performance and stability improvements, visual and spelling fixes have been done, too much to list all of them here. Check out all code changes of this release on GitHub: https://github.com/MichaIng/DietPi/pull/7900
 
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