Remove dev_finder.

We were copying dev_finder and device-finder as a transitional step
while updating flutter tools to use device-finder. Now that all the
tools have been updated we are ready to remove dev_finder.

Change-Id: I870f3f83ea761a5f420f1ebd19e0beab5cfc4622
Bug: fxb/55369
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/4060
Reviewed-by: Dan Field <dnfield@google.com>
Commit-Queue: Godofredo Contreras <godofredoc@google.com>