Remove uses of six and from __future__ imports as they are no longer needed. Change-Id: I74b5250722abe1e202f31a9ec1d4cc04039df168 Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/39757 Reviewed-by: Jason Lowe-Power <power.jg@gmail.com> Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu> Tested-by: kokoro <noreply+kokoro@google.com>