Refactor test teardown
Refactor test teardown

I saw a random (??) failure on the test on line 1098. This trivial chang
e just ensures that the configuration under test (the default
keybinding) is explicitly being set to `nil` after test runs.

gollum/gollum,repotag/gollum,repotag/gollum,gollum/gollum,rgroux/gollum,repotag/gollum,rgroux/gollum,gollum/gollum,repotag/gollum,rgroux/gollum,rgroux/gollum,repotag/gollum,gollum/gollum,gollum/gollum,rgroux/gollum