Update bioasq10b with name of test set data

When this code was originally written the test set for task 10b was not available. It is now available on the [BioASQ website](http://participants-area.bioasq.org/datasets/) so adding it to avoid an error when loading task 10b.

bioasq_task_b.py

@@ -380,7 +380,7 @@ _HOMEPAGE = "http://participants-area.bioasq.org/datasets/"
 _LICENSE = "NLM_LICENSE"
 
 _URLs = {
-    "bioasq_10b": ["BioASQ-training10b.zip", None],
+    "bioasq_10b": ["BioASQ-training10b.zip", "Task10BGoldenEnriched.zip"],
     "bioasq_9b": ["BioASQ-training9b.zip", "Task9BGoldenEnriched.zip"],
     "bioasq_8b": ["BioASQ-training8b.zip", "Task8BGoldenEnriched.zip"],
     "bioasq_7b": ["BioASQ-training7b.zip", "Task7BGoldenEnriched.zip"],