chore: update all source URLs for modules to reflect new namespace format

[Parkreiner]

No issue to link – it's meant to address feedback from the previous README PR

Changes made

• Updated all source properties in Terraform import snippets to use the new namespaced Terraform protocol URLs

Notes

• Probably need to wait until the latest version of the Registry website is pushed to production before we merge this in, just to be on the safe side
• I replaced all the paths via a regex, and then double-checked all the files modified to make sure there weren't any false positives

[matifali]

Thanks. Lets 🚢 it