fix(ingest): float proj issue

[slesaad]

What

Fixes the float epsg code issue caused by dynamodb serialization

Picked up the fix from developmentseed/eoapi-cdk#26

How test

Tested by running ingest from here: https://mv5tl66nca.execute-api.us-west-2.amazonaws.com/
Test item: https://vr3ofct5u8.execute-api.us-west-2.amazonaws.com/api/stac/collections/geoglam/items/CropMonitor_202205_test_2

import pystac

item = pystac.Item.from_file("https://vr3ofct5u8.execute-api.us-west-2.amazonaws.com/api/stac/collections/geoglam/items/CropMonitor_202205_test_2")
print(item.properties["proj:epsg"]) # should give 4326 instead of 4326.0

4326