Update data access and example data when NISAR L2 GCOV data release

[Alex-Lewandowski]

NISAR L2 GCOV data are not yet released, so this Cookbook has been developed with NISAR sample data.

Without production data available:

• Example data searches return no results
• Example workflows expect previously downloaded sample data, and then produce meaningless results

After production NISAR GCOV data are released:

• Confirm that all searches return products
• Update data recipes to pull and run on production data
  • Update annotations to refer to the data and AOI being examined