Remove Spin Up Hub content

[vdice]

• Remove the Spin Up Hub content under content/api/hub
• Remove other artifacts related to the Hub

Depends on

• spin.toml: update spin-related redirects #1490
• update spinframework.dev to reflect docs in this repo spinframework/spin-docs#11
• feat: add fwf examples spinframework/spin-docs#47
• Spin Up Hub search not working spinframework/spin-docs#91

[vdice]

Just want to get final approval from @flynnduism @mikkelhegn @macolso that we do indeed want to remove the Developer version of the Spin Up Hub, thus treating https://spinframework.dev/hub as the One ™️ True ™️ Spin Up Hub moving forward.

[mikkelhegn]

Sounds good. As long as we keep the link on developer.fermyon.com, and just directs to the new home.