[Pdr] Reconcile pdr-related docs with docs.predictoor.ai

[trentmc]

Background

Traditionally we've had Predictoor docs at https://docs.oceanprotocol.com. But we're moving them to https://docs.predictoor.ai, being served up by pdr-docs repo. Epic: pdr-docs#9.

Once that's live, we need to clean up predictoor-related docs in this repo.

Pre-requisite

docs.oceanprotocol.com must be live.

TODOs

• [x] update predictoor/README.md to just (a) a one-liner of what predictoor is (b) "Predictoor docs are now at predictoor.ai"
• [x] in SUMMARY.md, remove all but predictoor/README.md
• [x] in non-predictoor pages that point to predictoor docs, redirect to predictoor/README.md
• [x] update .gitbook.yaml: add redirects for each predictoor-related page to predictoor/README
• [x] in predictoor/ directory, delete all files except predictoor/README.md
• [x] in assets directory, delete all images used solely by predictoor