[recipes] Remove core.setup()

Each recipe now includes its own setup steps.

Bug: skia:6473
Change-Id: I97eab2cd63f5004c07408e844cbbed735aac355f
Reviewed-on: https://skia-review.googlesource.com/125660
Commit-Queue: Eric Boren <borenet@google.com>
Reviewed-by: Ben Wagner <benjaminwagner@google.com>