`modelfree.utils.sacred_copy` no longer necessary

[shwang]

adversarial-policies/src/modelfree/common/utils.py

Line 44 in 3a273ea

# TODO(adam): delete this once Sacred issue #498 is resolved

IDSIA/sacred#498 was resolved.

[AdamGleave]

The bug is still present in 0.7.5, I think we need to wait for Sacred 0.7.6 to come out.

[AdamGleave]

Although Sacred 0.8.x is now out, unfortunately we still need this because of IDSIA/sacred#499