Fix formatting via Black

Author: cslecrone

trio/_core/_thread_cache.py

@@ -58,7 +58,7 @@ def __init__(self, thread_cache):
 
     def _handle_job(self):
         # Handle job in a separate method to ensure user-created
-        # objects are cleaned up in a consistent manner. 
+        # objects are cleaned up in a consistent manner.
         fn, deliver = self._job
         self._job = None
         result = outcome.capture(fn)