Warnings in proper_unstack

[crusaderky]

Tests for proper_unstack triggers two warnings in xarray.
They've been temporarily suppressed but need to be looked at:

xarray_extras/xarray_extras/tests/test_stack.py

Lines 8 to 12 in 5fe7496

	# FIXME https://github.com/crusaderky/xarray_extras/issues/33
	pytestmark = pytest.mark.filterwarnings(
	"ignore:Updating MultiIndexed coordinate .* would corrupt indices",
	"ignore:invalid value encountered in cast:RuntimeWarning",
	)

[crusaderky]

This module is vendored in ndcsv and recursive_diff too.

There, there's 2 additional warnings (probably due to different dependencies?)

'ignore:the `pandas.MultiIndex` object.* will no longer be implicitly promoted:FutureWarning',
'ignore:updating coordinate .* with a PandasMultiIndex:FutureWarning',