Edge case: binary masking Landsat can fail when using a chunked lazy-loading array from stackstac

The code at lectures/11_stackstac.ipynb can fail when using a chunked lazy-loading array from stackstac. Moving the chunking to after the function fixes this issue, but it is worth being aware of. This most likely has to do with Dask being unable to infer the dimensions of the array after the bitmasking.