add redirect

Author: rushabh-v

doc/redirects.csv

@@ -1380,6 +1380,7 @@ generated/pandas.unique,../reference/api/pandas.unique
 generated/pandas.util.hash_array,../reference/api/pandas.util.hash_array
 generated/pandas.util.hash_pandas_object,../reference/api/pandas.util.hash_pandas_object
 generated/pandas.wide_to_long,../reference/api/pandas.wide_to_long
+reference/api/pandas.core.window.Rolling,../reference/api/pandas.core.window.rolling.Rolling.apply
 
 # Cached searches
 reference/api/pandas.DataFrame.from_csv,pandas.read_csv