Remove superfluous call to bool() (#9986)

Our strtobool already returns a bool, so no need to re-cast here

Signed-off-by: Dan Callahan <danc@element.io>

changelog.d/9986.misc

+Simplify a few helper functions.

synapse/config/registration.py

@@ -349,4 +349,4 @@ class RegistrationConfig(Config):
 
     def read_arguments(self, args):
         if args.enable_registration is not None:
-            self.enable_registration = bool(strtobool(str(args.enable_registration)))
+            self.enable_registration = strtobool(str(args.enable_registration))