Remove solum-builder-api from setup.cfg
Remove solum-builder-api from setup.cfg

There's no solum.cmd.builder:main at all.
Cleanup it.

Change-Id: I28e39f0d8756e7dba9dad93bc596abf99c7ef9f4

openstack/solum,stackforge/solum,stackforge/solum,openstack/solum