Use https URL in license file

Now that Causes is https everywhere, we may as well prevent a redirect
for those following this URL.

Change-Id: I26c52f36774a891a89eabe5f41f4e2946b205dca
Reviewed-on: https://gerrit.causes.com/31476
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>