remove blackpill

Author: hierophect

.github/workflows/build.yml

@@ -150,7 +150,6 @@ jobs:
         - "sparkfun_samd21_dev"
         - "sparkfun_samd21_mini"
         - "spresense"
-        - "stm32f411ce_blackpill"
         - "stm32f411ve_discovery"
         - "stm32f412zg_discovery"
         - "stringcar_m0_express"