CLN: Remove stray unicode_literals imports

These should have been removed when Python 2 support was dropped in
68c82be (gh-374, 2019-02-18).

Author: kyleam

reproman/distributions/vcs.py

@@ -8,8 +8,6 @@
 # ## ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 """Classes to identify VCS repos for files"""
 
-from __future__ import unicode_literals
-
 import abc
 import attr
 import os

reproman/interface/retrace.py

@@ -9,8 +9,6 @@
 """Analyze existing spec or session file system to gather more detailed information
 """
 
-from __future__ import unicode_literals
-
 from os.path import normpath
 import sys
 import time