Remove unnecessary Python 2 __future__ imports across 52+ files

[kredd2506]

Description

Over 52 files in models/official/ still contain Python 2 compatibility imports:

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

These have been unnecessary since Python 3.0 (2008) and are pure dead code.

Affected areas

• models/official/efficientnet/ (multiple files)
• models/official/detection/ (multiple files)
• models/official/amoeba_net/ (multiple files)
• models/official/resnet/
• models/official/densenet/
• models/official/mnist/
• And others across models/official/

Impact

• Adds visual noise to every file
• Signals to users that the codebase may still target Python 2, causing confusion
• Inconsistent — some files have them, others don't

Suggested Fix

Remove all from __future__ import statements across the codebase since Python 2 is long past end-of-life (Jan 2020).