Update repositories.txt (#4544)

https://github.com/adafruit/Adafruit_HX711

Author: ladyada

repositories.txt

@@ -244,6 +244,7 @@ https://github.com/adafruit/Adafruit_HTS221
 https://github.com/adafruit/Adafruit_HTU21DF_Library
 https://github.com/adafruit/Adafruit_HTU31D
 https://github.com/adafruit/Adafruit_HUSB238
+https://github.com/adafruit/Adafruit_HX711
 https://github.com/adafruit/Adafruit_HX8357_Library
 https://github.com/adafruit/Adafruit_ICM20X
 https://github.com/adafruit/Adafruit_ILI9341