[roottest] Remove from __future__ imports in Python tests

We only support Python 3 anyway.

Author: guitargeek

roottest/python/cling/force_flush.py

@@ -1,4 +1,2 @@
-from __future__ import print_function
-
 def print_flushed(*args):
    return print(*args, flush=True)

roottest/python/cmdLineUtils/testPatternToFileNameAndPathSplitList.py

@@ -1,8 +1,4 @@
 #!/usr/bin/python
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 """Test module for pattern to tuple"""
 

roottest/python/regression/pythonlib.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 import distutils.sysconfig as conf, sys, os; 
 ldlib = conf.get_config_var('LDLIBRARY')
 if ldlib: