Update doctsring to reflect temporalio/temporal#5946

Author: dandavison

temporalio/exceptions.py

@@ -117,8 +117,7 @@ def next_retry_delay(self) -> Optional[timedelta]:
         """Delay before the next activity retry attempt.
 
         User activity code may set this when raising ApplicationError to specify
-        a delay before the next activity retry. Ignored if set when raising
-        ApplicationError from workflow code.
+        a delay before the next activity retry.
         """
         return self._next_retry_delay