DOC: Updated reference link for resample method (#6735)

Author: pierre-manchon

xarray/core/common.py

@@ -1200,7 +1200,7 @@ def resample(
 
         References
         ----------
-        .. [1] http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases
+        .. [1] https://pandas.pydata.org/docs/user_guide/timeseries.html#dateoffset-objects
         """
         # TODO support non-string indexer after removing the old API.