Remove fake NWP data

[confusedmatrix]

Pull Request

• Removes fake NWP data
• The zarr now passed as NWP_ZARR_PATH is expected to be real and with correct timestamps

TODO

• [ ] Test with real NWP zarr in S3

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [ ] Yes

Checklist:

• [x] My code follows OCF's coding style guidelines
• [x] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] I have checked my code and corrected any misspellings