HLS2 STAC scientific extension implementation

[ghidalgo3]

Description

The 2 HLS2 collections claimed they implemented the STAC scientific extension, but they did not. Their items did, but the collections did not.

Previously, this would throw a validation error:

import pystac_client

pc_client = pystac_client.Client.open("https://planetarycomputer.microsoft.com/api/stac/v1/")
hls2_s30 = pc_client.get_collection("hls2-l30")
print(hls2_s30.validate())