Remove extra platform_packages line

ini/stm32f1.ini

 platform      = ${common_stm32f1.platform}
 extends       = common_stm32f1
 board         = genericSTM32F103RC
-platform_packages = tool-stm32duino
 extra_scripts = ${common_stm32f1.extra_scripts}
   buildroot/share/PlatformIO/scripts/mks_robin_e3.py
 build_flags   = ${common_stm32f1.build_flags}