Update fermyon/spin to spinframework/spin

[kate-goldenring]

Updates all references to fermyon/spin to spinframework/spin where needed.
Most links redirect and do not direly need updating. The following were broken unless updated

• python and js sdks docs have been moved as they were GitHub pages sites: (https://spinframework.github.io/spin-python-sdk/redis.html)
• references to old raw release artifacts

The following cases were not updated:

• kv-explorer (still under fermyon)
• static-fileserver (still under fermyon)
• cloud-gpu (under fermyon)
• Go SDK has not been republished to a new org -- none of these should be updated: import { Variables } from '@fermyon/spin-sdk';