DOC: fix link to io.zarr (#5176)

* DOC: fix link to io.zarr

* try ref

* Update xarray/core/dataset.py [skip-ci]

Co-authored-by: keewis <[email protected]>

Co-authored-by: keewis <[email protected]>

Author: raybellwaves

xarray/core/dataset.py

@@ -1849,7 +1849,8 @@ def to_zarr(
 
         See Also
         --------
-        http://xarray.pydata.org/en/stable/io.html#zarr
+        :ref:`io.zarr`
+            The I/O user guide, with more details and examples.
         """
         from ..backends.api import to_zarr