Remove pep8 target
Remove pep8 target

The target is now part of the linters environment, so can be
removed.

Change-Id: I825560b0d83541c0ca1a970f5f9ae9e6a4aeff71
Depends-On: If398a3e0415b2a0ab7f05ce390c18d9b28a85927

jianghuaw/os-ext-testing,BobBall/os-ext-testing,LinziWang/itri-peregrine-ci,yljh21328/project-config-example-trusty,citrix-openstack/os-ext-testing,jianghuaw/os-ext-testing,BobBall/os-ext-testing,LinziWang/itri-peregrine-ci,LinziWang/itri-peregrine-ci-0523,LinziWang/itri-peregrine-ci-0523,yljh21328/project-config-example-trusty,citrix-openstack/os-ext-testing