ItemCollection.to_xarray() fails when loading Item Collection from file

When loading an item collection from file, to_xarray leads to an error:

from simplestac.utils import ItemCollection

col = ItemCollection.from_file(col_file)
col.to_xarray()
# ValueError: Cannot pick a common CRS, since asset 'AOT' of item 0 'S2A_MSIL2A_20220120T105351_R051_T31UFQ_20220121T110346' does not have one.
# Please specify a CRS with the `epsg=` argument.

This issue comes from the fact that pystac >= 1.12 pops systematically the field proj:epsg when migrating to latest projection extension (2.0.0).

But in the case of an item with projection extension 1.2.0 it does not update the extension schema uri to 2.0.0 ...