Remove get_test function in test_expectations_unittest.py

Removed get_test function because it is simple enough to reference the test directly.

Review URL: https://codereview.chromium.org/669663002

git-svn-id: svn://svn.chromium.org/blink/trunk@183999 bbb929c8-8fbe-4397-9dbb-9b2b20218538