Unpin lazy-object-proxy for Python 2 (#469)

We moved away from Travis in #463.

Version pinning specific to Travis can be removed.

Author: pietern

dev-requirements-py2.txt

@@ -4,9 +4,3 @@ pylint-django<2.0
 pep8-naming==0.5.0
 flake8<3.5
 pyflakes<1.6.0,>=1.5.0
-
-# For some reason Travis tries to install the yanked version 1.7.0.
-# See https://pypi.org/project/lazy-object-proxy/#history.
-# See https://github.com/databricks/databricks-cli/pull/462.
-# Try to unpin this after moving away from Travis.
-lazy-object-proxy==1.6.0