Bump dev version (#5808)

Author: github-actions[bot]

cylc/flow/__init__.py

@@ -53,7 +53,7 @@ def environ_init():
 
 environ_init()
 
-__version__ = '8.2.3'
+__version__ = '8.2.4.dev'
 
 
 def iter_entry_points(entry_point_name):