Update black, and run auto formatting over the codebase (#9381)

- Update black version to the latest
 - Run black auto formatting over the codebase
    - Run autoformatting according to [`docs/code_style.md
`](80d6dc9783/docs/code_style.md)
 - Update `code_style.md` docs around installing black to use the correct version

synapse/types.py

@@ -469,8 +469,7 @@ class RoomStreamToken:
     )
 
     def __attrs_post_init__(self):
-        """Validates that both `topological` and `instance_map` aren't set.
-        """
+        """Validates that both `topological` and `instance_map` aren't set."""
 
         if self.instance_map and self.topological:
             raise ValueError(
@@ -498,7 +497,11 @@ class RoomStreamToken:
                     instance_name = await store.get_name_from_instance_id(instance_id)
                     instance_map[instance_name] = pos
 
-                return cls(topological=None, stream=stream, instance_map=instance_map,)
+                return cls(
+                    topological=None,
+                    stream=stream,
+                    instance_map=instance_map,
+                )
         except Exception:
             pass
         raise SynapseError(400, "Invalid token %r" % (string,))