Remove __future__ imports once Python 3 conversion is complete

[nrejac]

Given that Python 2.x will not be supported in the future, we expect the released version of idb-backend for Python 3 to use standard Python 3 behavior: print is a function, integer division can return floats, absolute imports are allowed, etc.

For simplicity, we can then remove future imports that enable Python 3 behavior under prior versions of the Python interpreter and the Python interpreter will continue use standard Python 3 behavior. The code will not run successfully on Python 2.

[danstoner]

I generally agree with the sentiment.

https://stackoverflow.com/a/53831042

We will need to make sure we are only removing the python 2 futures (most likely).

Also in that SO article... barry_as_FLUFL!

https://www.python.org/dev/peps/pep-0401/