Remove st2client from requirements
Remove st2client from requirements

* st2client should end up being available via system dependencies.

StackStorm/st2contrib,armab/st2contrib,pidah/st2contrib,pearsontechnology/st2contrib,pidah/st2contrib,armab/st2contrib,pidah/st2contrib,armab/st2contrib,StackStorm/st2contrib,pearsontechnology/st2contrib,tonybaloney/st2contrib,pearsontechnology/st2contrib,pearsontechnology/st2contrib,psychopenguin/st2contrib,tonybaloney/st2contrib,StackStorm/st2contrib,psychopenguin/st2contrib,tonybaloney/st2contrib