In traitsui, traitsui.__version__ has been deprecated and should be
replaced with importlib.metadata.version('traitsui'). The deprecation
warning raised have also caused test_edit_not_given in
traits/traits/tests/test_configure_traits.py to fail as mentioned in
#1745 . Since the version check is a temporary check to address the
dependency of traits on traits ui and is no longer need, the current PR
fixed this issue by removing all version checks related to
_traitsui_helpers.py.

Closes #1745

Co-authored-by: Chengyu Liu <[email protected]>
(cherry picked from commit 60f918e)

This PR fixes one part of the cause of #1748, namely that a test was
failing on warnings that were unrelated to the test purpose.

(cherry picked from commit d066c6d)

…on 3.6