Use dashes instead of underscores for METADATA.toml field names (#15614)

stubs/RPi.GPIO/METADATA.toml

@@ -1,10 +1,10 @@
 version = "0.7.*"
-upstream_repository = "https://sourceforge.net/p/raspberry-gpio-python/code/"
+upstream-repository = "https://sourceforge.net/p/raspberry-gpio-python/code/"
 
 [tool.stubtest]
 # This package is only supported on Raspberry Pi hardware, which identifies
 # itself as 'linux'. When run on other hardware, it raises a RuntimeError:
 # RPi.GPIO failed to import. RuntimeError: This module can only be run on a Raspberry Pi!
 # https://sourceforge.net/p/raspberry-gpio-python/code/ci/08048dd1894a6b09a104557b6eaa6bb68b6baac5/tree/source/py_gpio.c#l1008
-supported_platforms = []
-ci_platforms = []
+supported-platforms = []
+ci-platforms = []