Fix reference to Embedding Appendix in tutorial documentation

[JonathanRayner]

Currently the tutorial embedding data docs have a broken link and point to Appendix 3. I think it should point to Appendix 2.

Test Plan:
skipped: just updating docs.

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[JonathanRayner]

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[JonathanRayner]

recheck

[JonathanRayner]

bad bot :)