Rechunking error when saving a queried raster element

[LucaMarconato]

As reported here, https://github.com/scverse/spatialdata-io/issues/117 querying a raster element and trying to save it may lead to the following error:

ValueError: Attempt to save array to zarr with irregular chunking, please call `arr.rechunk(...)` first.

A solution is to rechunk the data, I will make a fix for this.