PYTHON-5505 Fix _retry_overload handling of backoff too

Author: ShaneHarvey

pymongo/asynchronous/helpers.py

@@ -105,7 +105,8 @@ async def inner(*args: Any, **kwargs: Any) -> Any:
                     raise
 
                 # Implement exponential backoff on retry.
-                await _backoff(attempt)
+                if exc.has_error_label("SystemOverloaded"):
+                    await _backoff(attempt)
                 continue
 
     return cast(F, inner)

pymongo/synchronous/helpers.py

@@ -105,7 +105,8 @@ def inner(*args: Any, **kwargs: Any) -> Any:
                     raise
 
                 # Implement exponential backoff on retry.
-                _backoff(attempt)
+                if exc.has_error_label("SystemOverloaded"):
+                    _backoff(attempt)
                 continue
 
     return cast(F, inner)