Remove "BULLM-Extend-Motor" from repository list

A duplicate copy of the library was submitted rather than following the standard procedure for requesting a name change
request.

The presence of this entry no longer serves any value and only clutters up Library Manager.

Author: per1234

repositories.txt

@@ -8206,7 +8206,6 @@ https://github.com/HS3UKA/HS3UKA_PCF8574
 https://github.com/muhpuc40/MacRandomizer
 https://github.com/faisalill/BMP390
 https://github.com/SpaceTrekKSC/MakerBox
-https://github.com/bull-m/BULLM-Extend-Motor
 https://github.com/BackLogers/RYUW122_UWB
 https://github.com/LCerimeli/StratoLit-BQ25611D
 https://github.com/gly-engine/core-native-arduino