renumber_migrations: Strip trailing '.py' from migrations.
renumber_migrations: Strip trailing '.py' from migrations.

This fixes a bug when renumbering more than 1 migration at a time.

rishig/zulip,jphilipsen05/zulip,ryanbackman/zulip,ryanbackman/zulip,ryanbackman/zulip,punchagan/zulip,kou/zulip,brockwhittaker/zulip,jrowan/zulip,rishig/zulip,zulip/zulip,timabbott/zulip,zulip/zulip,tommyip/zulip,synicalsyntax/zulip,andersk/zulip,j831/zulip,brockwhittaker/zulip,verma-varsha/zulip,showell/zulip,Galexrt/zulip,eeshangarg/zulip,j831/zulip,brockwhittaker/zulip,rishig/zulip,hackerkid/zulip,zulip/zulip,andersk/zulip,synicalsyntax/zulip,shubhamdhama/zulip,shubhamdhama/zulip,jphilipsen05/zulip,verma-varsha/zulip,rishig/zulip,mahim97/zulip,ryanbackman/zulip,rishig/zulip,brainwane/zulip,synicalsyntax/zulip,christi3k/zulip,j831/zulip,timabbott/zulip,tommyip/zulip,brainwane/zulip,amanharitsh123/zulip,rht/zulip,jphilipsen05/zulip,andersk/zulip,j831/zulip,synicalsyntax/zulip,shubhamdhama/zulip,ryanbackman/zulip,jackrzhang/zulip,hackerkid/zulip,rishig/zulip,brainwane/zulip,punchagan/zulip,dhcrzf/zulip,eeshangarg/zulip,jphilipsen05/zulip,rishig/zulip,hackerkid/zulip,jackrzhang/zulip,brockwhittaker/zulip,amanharitsh123/zulip,vaidap/zulip,dhcrzf/zulip,shubhamdhama/zulip,Galexrt/zulip,mahim97/zulip,punchagan/zulip,synicalsyntax/zulip,vabs22/zulip,eeshangarg/zulip,SmartPeople/zulip,jrowan/zulip,eeshangarg/zulip,jackrzhang/zulip,vaidap/zulip,rht/zulip,amanharitsh123/zulip,mahim97/zulip,vabs22/zulip,amanharitsh123/zulip,jphilipsen05/zulip,kou/zulip,andersk/zulip,jackrzhang/zulip,ryanbackman/zulip,zulip/zulip,hackerkid/zulip,hackerkid/zulip,punchagan/zulip,andersk/zulip,vaidap/zulip,rht/zulip,SmartPeople/zulip,brainwane/zulip,showell/zulip,timabbott/zulip,kou/zulip,kou/zulip,jackrzhang/zulip,mahim97/zulip,tommyip/zulip,timabbott/zulip,Galexrt/zulip,jrowan/zulip,Galexrt/zulip,shubhamdhama/zulip,amanharitsh123/zulip,jrowan/zulip,jackrzhang/zulip,jackrzhang/zulip,eeshangarg/zulip,rht/zulip,verma-varsha/zulip,brainwane/zulip,jphilipsen05/zulip,vabs22/zulip,eeshangarg/zulip,dhcrzf/zulip,Galexrt/zulip,brockwhittaker/zulip,punchagan/zulip,showell/zulip,mahim97/zulip,dhcrzf/zulip,rht/zulip,dhcrzf/zulip,verma-varsha/zulip,kou/zulip,eeshangarg/zulip,SmartPeople/zulip,vaidap/zulip,kou/zulip,timabbott/zulip,verma-varsha/zulip,jrowan/zulip,timabbott/zulip,tommyip/zulip,christi3k/zulip,synicalsyntax/zulip,showell/zulip,christi3k/zulip,vabs22/zulip,dhcrzf/zulip,rht/zulip,SmartPeople/zulip,andersk/zulip,dhcrzf/zulip,vabs22/zulip,timabbott/zulip,shubhamdhama/zulip,tommyip/zulip,showell/zulip,amanharitsh123/zulip,andersk/zulip,brainwane/zulip,verma-varsha/zulip,christi3k/zulip,vaidap/zulip,zulip/zulip,zulip/zulip,kou/zulip,vabs22/zulip,synicalsyntax/zulip,j831/zulip,jrowan/zulip,brockwhittaker/zulip,vaidap/zulip,SmartPeople/zulip,punchagan/zulip,punchagan/zulip,tommyip/zulip,Galexrt/zulip,rht/zulip,showell/zulip,Galexrt/zulip,hackerkid/zulip,showell/zulip,tommyip/zulip,christi3k/zulip,hackerkid/zulip,brainwane/zulip,christi3k/zulip,SmartPeople/zulip,mahim97/zulip,j831/zulip,shubhamdhama/zulip,zulip/zulip