Update interpolate_na in dataset.py (#7974)

* Update interpolate_na in dataset.py

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* Update xarray/core/dataset.py

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Deepak Cherian <[email protected]>

Author: 3 people

xarray/core/dataset.py

@@ -6083,6 +6083,11 @@ def interpolate_na(
         interpolated: Dataset
             Filled in Dataset.
 
+        Warning
+        --------
+        When passing fill_value as a keyword argument with method="linear", it does not use
+        ``numpy.interp`` but it uses ``scipy.interpolate.interp1d``, which provides the fill_value parameter.
+
         See Also
         --------
         numpy.interp