[Core] Show fewer warnings when using environment variable auth

Author: VoxSecundus

src/azure-cli-core/azure/cli/core/_profile.py

@@ -612,7 +612,7 @@ def get_subscription(self, subscription=None, allow_null_subscription=False):  #
 
         # Attempt to use env vars
         if env_var_auth_configured():
-            logger.warning("Using subscription configured in environment variables.")
+            logger.debug("Using subscription configured in environment variables.")
             env_var_sub = load_env_var_subscription()
             if subscription:
                 # Subscription ID must be a GUID

src/azure-cli-core/azure/cli/core/auth/identity.py

@@ -312,7 +312,7 @@ def load_entry(self, sp_id, tenant):
 
         # If no login data, look for service principal credential in environment variables
         if not self._entries and env_var_auth_configured():
-            logger.warning("Using service principal credential configured in environment variables.")
+            logger.debug("Using service principal credential configured in environment variables.")
             self._entries = [load_env_var_credential()]
 
         matched = [x for x in self._entries if sp_id == x[_CLIENT_ID]]