Fix issue in sentinel 2 metadata where 0 z coordinates are listed.

There are some produt metadata files that contain 0 z coordinate
values in the product metadata that is used to construct STAC Item
geometries. This causes the Item geometry to be invalid. This change
modifies the parsing logic to filter out '0' string values in the
coordinates to avoid this issue.

stactools_sentinel2/stactools/sentinel2/product_metadata.py

@@ -69,8 +69,11 @@ def _get_geometries():
                 ProductMetadataError(
                     f'Cannot parse footprint from product metadata at {self.href}'
                 )
+
+            # Some coordinates contain a 0 z dimension for some reason;
+            # filter those out
             footprint_coords = [
-                float(c) for c in footprint_text.split(' ') if c
+                float(c) for c in footprint_text.split(' ') if c and c != '0'
             ]
             footprint_points = [
                 p[::-1] for p in list(zip(*[iter(footprint_coords)] * 2))