runner: Remove unused import

The "import multiprocessing.queues" results in imported
"multiprocessing".
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

avocado/core/runner.py

@@ -17,7 +17,6 @@
 Test runner module.
 """
 
-import multiprocessing
 import multiprocessing.queues
 import os
 import signal