removed comma at the end of sentence

Author: arthurlw

pandas/core/groupby/groupby.py

@@ -3815,7 +3815,7 @@ def expanding(self, *args, **kwargs) -> ExpandingGroupby:
         *args : tuple
             Positional arguments passed to the expanding window constructor.
         **kwargs : dict
-            Keyword arguments passed to the expanding window constructor,
+            Keyword arguments passed to the expanding window constructor.
 
         Returns
         -------