temporarily silence shape assignment warnings raised in netCDF4

[keewis]

• towards closing ⚠️ Nightly upstream-dev CI failed ⚠️ #11051

Apparently, numpy has decided to deprecate assignments like x[...] = y. We can replace this with

slices = (slice(None),) * y.ndim
x[slices] = y

[jsignell]

Gross but good catch! It looks like there is another assignment like this in _copy_with_dtype

[keewis]

I might have totally misunderstood what they deprecated. It appears that was x.shape = new_shape, not ellipsis assignment. However, that means that the warning would actually be emitted in netcdf4 code, so I'm trying to create a reproducer without using xarray code.

Edit: see Unidata/netcdf4-python#1468

[keewis]

should be good for another round of reviews (I'm not at all sure this is the best way to ignore the warning) and merging

[jsignell]

LGTM!

[keewis]

let's merge, then!