Remove hardcoded version for pep8 from tools/test-requires
Remove hardcoded version for pep8 from tools/test-requires

In email discussions we decided that the master branch should always
pull in the lastest version of the pep8 tool, which keeps us closest
to the real pep-8 document.  Therefore, I'm removing the hardcoded
version here to match the lack of a pep8 version in tox.ini (which is
what the CI infrastructure uses when running the gating pep8 checks).

Note that your pep8 version will only update when you re-run
pip install --upgrade -r tools/test-requires .

Change-Id: I242cb042cff5f5969aa50d40312f87979191c7b7

asgard-lab/neutron,projectcalico/calico-neutron,bgxavier/neutron,swdream/neutron,yamt/neutron,Juniper/neutron,blueboxgroup/neutron,eonpatapon/neutron,CiscoSystems/vespa,watonyweng/neutron,leeseuljeong/leeseulstack_neutron,netscaler/neutron,huntxu/neutron,savi-dev/quantum,psiwczak/quantum,eonpatapon/neutron,zhhf/charging,vivekanand1101/neutron,apporc/neutron,ykaneko/quantum,tpaszkowski/quantum,SmartInfrastructures/neutron,antonioUnina/neutron,gkotton/neutron,yamahata/tacker,chitr/neutron,eayunstack/neutron,skyddv/neutron,jerryz1982/neutron,leeseuljeong/leeseulstack_neutron,Juniper/neutron,ykaneko/quantum,Metaswitch/calico-neutron,takeshineshiro/neutron,yamahata/tacker,armando-migliaccio/neutron,yanheven/neutron,xchenum/quantum-bug,ykaneko/neutron,ykaneko/quantum,huntxu/neutron,sajuptpm/neutron-ipam,Metaswitch/calico-neutron,aristanetworks/arista-ovs-quantum,rossella/neutron,suneeth51/neutron,rossella/neutron,savi-dev/quantum,glove747/liberty-neutron,watonyweng/neutron,vveerava/Openstack,yamahata/neutron,CiscoSystems/vespa,ykaneko/neutron,tpaszkowski/quantum,yamt/neutron,mandeepdhami/neutron,javaos74/neutron,miyakz1192/neutron,rdo-management/neutron,cloudbase/neutron,igor-toga/local-snat,noironetworks/neutron,sajuptpm/neutron-ipam,silenci/neutron,CiscoSystems/neutron,adelina-t/neutron,liqin75/vse-vpnaas-plugin,FreescaleSemiconductor/quantum,kaiweifan/vse-lbaas-plugin-poc,Stavitsky/neutron,JianyuWang/neutron,openstack/neutron,vbannai/neutron,eayunstack/neutron,sebrandon1/neutron,Comcast/neutron,mattt416/neutron,kaiweifan/vse-lbaas-plugin-poc,kaiweifan/neutron,suneeth51/neutron,neoareslinux/neutron,antonioUnina/neutron,dhanunjaya/neutron,JioCloud/neutron,aristanetworks/neutron,CiscoSystems/quantum,rossella/neutron,javaos74/neutron,CiscoSystems/quantum,tpaszkowski/quantum,leeseulstack/openstack,CiscoSystems/vespa,gopal1cloud/neutron,SmartInfrastructures/neutron,magic0704/neutron,yanheven/neutron,FreescaleSemiconductor/quantum,Brocade-OpenSource/OpenStack-DNRM-Neutron,yamahata/neutron,wenhuizhang/neutron,sasukeh/neutron,mmnelemane/neutron,Brocade-OpenSource/OpenStack-DNRM-Neutron,kaiweifan/neutron,Comcast/neutron,NeCTAR-RC/neutron,virtualopensystems/neutron,virtualopensystems/neutron,yuewko/neutron,liqin75/vse-vpnaas-plugin,SamYaple/neutron,Juniper/neutron,vijayendrabvs/ssl-neutron,ykaneko/quantum,asgard-lab/neutron,redhat-openstack/neutron,Brocade-OpenSource/OpenStack-DNRM-Neutron,ntt-sic/neutron,infobloxopen/neutron,liqin75/vse-vpnaas-plugin,bgxavier/neutron,FreescaleSemiconductor/quantum,jacknjzhou/neutron,CiscoSystems/neutron,miyakz1192/neutron,mandeepdhami/neutron,psiwczak/quantum,cernops/neutron,paninetworks/neutron,klmitch/neutron,ykaneko/neutron,MaximNevrov/neutron,gkotton/neutron,alexandrucoman/vbox-neutron-agent,barnsnake351/neutron,jumpojoy/neutron,infobloxopen/neutron,skyddv/neutron,rickerc/neutron_audit,beagles/neutron_hacking,apporc/neutron,wolverineav/neutron,citrix-openstack-build/neutron,vijayendrabvs/hap,citrix-openstack-build/neutron,aristanetworks/neutron,dhanunjaya/neutron,shahbazn/neutron,silenci/neutron,dims/neutron,swdream/neutron,waltBB/neutron_read,leeseulstack/openstack,mattt416/neutron,CiscoSystems/quantum,cloudbase/neutron,sasukeh/neutron,savi-dev/quantum,openstack/neutron,redhat-openstack/neutron,beagles/neutron_hacking,mahak/neutron,neoareslinux/neutron,xchenum/quantum,Juniper/contrail-dev-neutron,virtualopensystems/neutron,NeCTAR-RC/neutron,barnsnake351/neutron,psiwczak/quantum,savi-dev/quantum,vijayendrabvs/hap,leeseulstack/openstack,kaiweifan/neutron,Juniper/contrail-dev-neutron,vijayendrabvs/hap,vijayendrabvs/ssl-neutron,magic0704/neutron,dims/neutron,blueboxgroup/neutron,xchenum/quantum,armando-migliaccio/neutron,adelina-t/neutron,mahak/neutron,xchenum/quantum-bug,mmnelemane/neutron,takeshineshiro/neutron,armando-migliaccio/neutron,CiscoSystems/neutron,yamahata/neutron,blueboxgroup/neutron,yamahata/tacker,yamt/neutron,rickerc/neutron_audit,vveerava/Openstack,netscaler/neutron,Stavitsky/neutron,ntt-sic/neutron,cisco-openstack/neutron,aristanetworks/arista-ovs-quantum,bigswitch/neutron,bigswitch/neutron,aristanetworks/arista-ovs-quantum,ntt-sic/neutron,vveerava/Openstack,paninetworks/neutron,cloudbase/neutron-virtualbox,tpaszkowski/quantum,sajuptpm/neutron-ipam,yuewko/neutron,FreescaleSemiconductor/quantum,rickerc/neutron_audit,glove747/liberty-neutron,Comcast/neutron,chitr/neutron,psiwczak/quantum,beagles/neutron_hacking,vivekanand1101/neutron,leeseuljeong/leeseulstack_neutron,jacknjzhou/neutron,MaximNevrov/neutron,xchenum/quantum-bug,citrix-openstack-build/neutron,openstack/neutron,pnavarro/neutron,JioCloud/neutron,shahbazn/neutron,liqin75/vse-vpnaas-plugin,kaiweifan/vse-lbaas-plugin-poc,gopal1cloud/neutron,jumpojoy/neutron,Juniper/contrail-dev-neutron,oeeagle/quantum,gkotton/neutron,mahak/neutron,SamYaple/neutron,klmitch/neutron,sebrandon1/neutron,vbannai/neutron,alexandrucoman/vbox-neutron-agent,waltBB/neutron_read,cloudbase/neutron-virtualbox,vbannai/neutron,xchenum/quantum,vijayendrabvs/ssl-neutron,zhhf/charging,kaiweifan/vse-lbaas-plugin-poc,armando-migliaccio/neutron,jerryz1982/neutron,cernops/neutron,rossella/neutron,wenhuizhang/neutron,igor-toga/local-snat,yamt/neutron,netscaler/neutron,rdo-management/neutron,JianyuWang/neutron,oeeagle/quantum,wolverineav/neutron,noironetworks/neutron,pnavarro/neutron,aristanetworks/arista-ovs-quantum,zhhf/charging,projectcalico/calico-neutron,cisco-openstack/neutron