Enable public client ROPC via broker. On Windows, ROPC will call WAM; on

macOS, ROPC will call MSAL C++ logic.

Author: fengga

msal/application.py

@@ -1710,7 +1710,7 @@ def acquire_token_by_username_password(
         """
         claims = _merge_claims_challenge_and_capabilities(
                 self._client_capabilities, claims_challenge)
-        if False:  # Disabled, for now. It was if self._enable_broker:
+        if self._enable_broker:
             from .broker import _signin_silently
             response = _signin_silently(
                 "https://{}/{}".format(self.authority.instance, self.authority.tenant),