Log Message:
py-xarray: updated to 0.20.2

v0.20.2

This is a bugfix release to resolve (:issue:`3391`, :issue:`5715`). It also
includes performance improvements in unstacking to a ``sparse`` array and a
number of documentation improvements.

Breaking changes
- Use complex nan when interpolating complex values out of bounds by default \ 
(instead of real nan) (:pull:`6019`).

Performance
- Significantly faster unstacking to a ``sparse`` array. :pull:`5577`

Bug fixes
- :py:func:`xr.map_blocks` and :py:func:`xr.corr` now work when dask is not \ 
installed (:issue:`3391`, :issue:`5715`, :pull:`5731`).
- Fix plot.line crash for data of shape ``(1, N)`` in _title_for_slice on \ 
format_item (:pull:`5948`).
- Fix a regression in the removal of duplicate backend entrypoints \ 
(:issue:`5944`, :pull:`5959`)

Documentation
- Better examples in docstrings for groupby and resampling reductions (:pull:`5871`).

Internal Changes
- Use ``importlib`` to replace functionality of ``pkg_resources`` in
  backend plugins tests. (:pull:`5959`).