stdlib: Remove unneeded imports in the gem5 Python Library

Change-Id: I6d4ccc4e18bd36d4a9dad9b6782ebcc0e64c4e44
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52203
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
5 files changed