Update repositories.txt (#5744)

Add https://github.com/RobTillaart/TCA9554 IO expander

Author: RobTillaart

repositories.txt

@@ -5560,6 +5560,7 @@ https://github.com/RobTillaart/Student
 https://github.com/RobTillaart/SWSerialOut
 https://github.com/RobTillaart/SWSPI
 https://github.com/RobTillaart/TCA9548
+https://github.com/RobTillaart/TCA9554
 https://github.com/RobTillaart/TCA9555
 https://github.com/RobTillaart/Temperature
 https://github.com/RobTillaart/TEMT6000