Use of `force_to_top` for `isort`

[jrbourbeau]

In dask/distributed#5170, @fjetter pointed out that distributed was incorrectly using force_to_top in our isort configuration (we should have been using float_to_top instead). Just a minor point, but since xarrays isort configuration influenced what we did over in dask and distributed, I thought it was worth letting the Xarray devs know about it

xarray/setup.cfg

Line 164 in 8f5b4a1

force_to_top = true

[max-sixty]

Thanks @jrbourbeau , agree.

Would take a PR if anyone is up for a short one...