improved docstring of to_netcdf (issue pydata#7127)

Author: vallirep

xarray/core/dataset.py

@@ -1919,7 +1919,9 @@ def to_netcdf(
             Nested dictionary with variable names as keys and dictionaries of
             variable specific encodings as values, e.g.,
             ``{"my_variable": {"dtype": "int16", "scale_factor": 0.1,
-            "zlib": True}, ...}``
+            "zlib": True}, ...}``.
+            If encoding is specified the original encoding of the variables of
+            the dataset is ingnored
 
             The `h5netcdf` engine supports both the NetCDF4-style compression
             encoding parameters ``{"zlib": True, "complevel": 9}`` and the h5py