Remove pick_ik as a dependency

[sea-bass]

Description

If people want to use pick_ik, it can still be installed optionally. But it's a bit wasteful to have it be built all the time.

Checklist

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[stephanie-eng]

Can we add a small reminder to this blurb in the pick_ik tutorial to install pick_ik before running the pre-configured example? We already have instructions in the tutorial on how to do it, but since it won't quite be "out-of-the box", wouldn't hurt to remind folks.

[stephanie-eng]

If you don't want to do the above, I can probably just do it in a future PR later, I'm also fine with this as-is.