Merge pull request #6140 from per1234/retire-Arduino_AVRSTL

Add "Retired" type to "Arduino_AVRSTL"

Author: MatteoPologruto

registry.txt

@@ -80,7 +80,7 @@ https://github.com/arduino-libraries/Arduino_MKRIoTCarrier.git|Arduino|Arduino_M
 https://github.com/arduino-libraries/Arduino_MCHPTouch.git|Arduino|Arduino_MCHPTouch
 https://github.com/arduino-libraries/Arduino_ScienceJournal.git|Arduino|Arduino_ScienceJournal
 https://github.com/arduino-libraries/Arduino_SensorKit.git|Arduino|Arduino_Sensorkit
-https://github.com/arduino-libraries/Arduino_AVRSTL.git|Arduino|Arduino_AVRSTL
+https://github.com/arduino-libraries/Arduino_AVRSTL.git|Arduino,Retired|Arduino_AVRSTL
 https://github.com/arduino-libraries/Arduino_Portenta_OTA.git|Arduino|Arduino_Portenta_OTA
 https://github.com/arduino-libraries/Arduino_Pro_Tutorials.git|Arduino|Arduino_Pro_Tutorials
 https://github.com/arduino-libraries/Arduino_EdgeControl.git|Arduino|Arduino_EdgeControl