Remove broken dependency
Remove broken dependency

  * [futures](https://pypi.org/project/futures/) is a backport to Python2
  of the `concurrent.futures` module in the Python3 standard library;
  * And angr does not support Python2 anymore.

angr/angr,iamahuman/angr,angr/angr,iamahuman/angr,schieb/angr,iamahuman/angr,schieb/angr,schieb/angr,angr/angr