Remove "always fail" test

tests/unit/test_app.py

@@ -11,10 +11,6 @@ from repo2docker.__main__ import make_r2d
 from repo2docker.utils import chdir
 
 
-def test_always_fails():
-    assert False
-
-
 def test_find_image():
     images = [{"RepoTags": ["some-org/some-repo:latest"]}]