Fix bug: remove duplicate call to initialize video
Fix bug: remove duplicate call to initialize video

Fix bug: remove duplicate `gtk.idle_add` call to
`DmfDeviceController._initialize_video`.

Prior to this commit, the code for the `DmfDeviceController` was changed
to wait until the GUI was ready before initializing the device view
video.  However, the duplicate call to `_initialize_video` causes video
initialization to fail (at least on Windows).

wheeler-microfluidics/microdrop