typo in action yaml 5

Author: askuric

.github/workflows/ccpp.yml

@@ -47,7 +47,7 @@ jobs:
             sketch-names: esp32_position_control.ino, esp32_i2c_dual_bus_example.ino, esp32_current_control_low_side.ino, esp32_spi_alt_example.ino
 
           - arduino-boards-fqbn: STMicroelectronics:stm32:GenF1:pnum=BLUEPILL_F103C8 # bluepill - hs examples
-            platform-url: https://github.com/stm32duino/BoardManagerFiles/raw/master/STM32/package_stm_index.json 
+            platform-url:  https://github.com/stm32duino/BoardManagerFiles/raw/main/package_stmicroelectronics_index.json 
             sketch-names: bluepill_position_control.ino, stm32_i2c_dual_bus_example.ino, stm32_spi_alt_example.ino
 
           - arduino-boards-fqbn: STMicroelectronics:stm32:GenF4:pnum=GENERIC_F405RGTX  # stm32f405 - odrive