update for existing 2020 grid code errors

[pholleway]

Current package returns grid code errors on subset of 2020 items.

• The grid code references the item id.
• Item Id references xml, which contains incorrect str format for item Id.

The errors are resolved by having the item id reference another section in the xml (gmd:fileIdentifier) with correct str format.

[philvarner]

Is there a test you can add?

[pholleway]

Is there a test you can add?

@philvarner

• added example data throwing the grid code error
• added a test on the example data in test_stac.py