meta: Bump new development version

setup.py

@@ -32,7 +32,7 @@ from sentry.utils.distutils import (
     BuildJsSdkRegistryCommand,
 )
 
-VERSION = "21.9.0"
+VERSION = "21.10.0.dev0"
 IS_LIGHT_BUILD = os.environ.get("SENTRY_LIGHT_BUILD") == "1"