Link to bugfix tree (#21263)

config/README.md

 
 Marlin configurations for specific machines are now maintained in their own repository at:
 
-## https://github.com/MarlinFirmware/Configurations
+## https://github.com/MarlinFirmware/Configurations/tree/bugfix-2.0.x
 
 Configuration files for use with the nightly `bugfix-2.0.x` branch can be downloaded from: