Remove old pins.py.
Remove old pins.py.

It's now at aiy/pins.py location.

Change-Id: I26ce18479c62c21cd40136f4aa0bef36bc768edb

google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian