MNT: remove plot_first_motor from _OuterProductScan
MNT: remove plot_first_motor from _OuterProductScan

These are 2+D scans, do not try to plot as 1D.

This removes a conflict with LiveRaster and LiveMesh

ericdill/bluesky,dchabot/bluesky,ericdill/bluesky,dchabot/bluesky