dirstate: re-blacken file

This got overlooked in landing a recent patch, but it's easy to fix up.

Differential Revision: https://phab.mercurial-scm.org/D7367

mercurial/dirstate.py

@@ -1114,7 +1114,9 b' class dirstate(object):'
             # how to read the config file.
             numcpus = self._ui.configint("worker", "numcpus")
             if numcpus is not None:
-                encoding.environ.setdefault(b'RAYON_NUM_THREADS', b'%d' % numcpus)
+                encoding.environ.setdefault(
+                    b'RAYON_NUM_THREADS', b'%d' % numcpus
+                )
 
             workers_enabled = self._ui.configbool("worker", "enabled", True)
             if not workers_enabled: