Update docs for Registry-based Terraform provider #14674
Description
We still have references to the pre-registry TF provider SDK on the following pages:
- https://www.pulumi.com/docs/iac/languages-sdks/javascript/#standard-packages (remove the link since the registry is the normal place people would look for any provider SDK)
- https://www.pulumi.com/docs/iac/languages-sdks/python/#standard-packages (ibid)
These need to be removed and we should instead direct users to the Registry.