fix: Python 3.11's change to IntEnum.__str__

Make a __str__ method for `JobStatus` which reverts back to printing out
the enum member's name.

flow/scheduling/base.py

@@ -101,6 +101,10 @@ def _to_group(cls, status):
         except KeyError:
             raise ValueError(f"No equivalent group status for {status}.")
 
+    def __str__(self):
+        """Get the status name as a string."""
+        return self.name
+
 
 class ClusterJob:
     """Class representing a cluster job."""