"Advanced Delving" refers to GM Principles that don't exist

[NerdyNathan]

The following are referred to as GM principles in "Advanced Delving" but are not found in the list of GM Principles in "GM"

• Make your move, but misdirect
• Give them something to work towards
• Sometimes, let them decide

I would open a pull request, but I'm not sure if these should be removed or replaced.

[Sagelt]

Yep, these are all old phrasings or AW principles that made it past early editing. Given that they're self-descriptive anyway and the text is very old at this point I don't think it's worth rewording, but something to be on the lookout for if we ever do significant updates.