Remove pep8 target

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

Change-Id: I825560b0d83541c0ca1a970f5f9ae9e6a4aeff71
Depends-On: If398a3e0415b2a0ab7f05ce390c18d9b28a85927

tox.ini

@@ -11,11 +11,6 @@ commands =
   flake8
   {toxinidir}/tools/run-bashate.sh
 
-[testenv:pep8]
-commands =
-  flake8
-  {toxinidir}/tools/run-bashate.sh
-
 [testenv:venv]
 commands = {posargs}