Change version string to comply with PEP440

It seems "-dev" (normalized to ".dev") should only be directly followed
by a number for different deveopment releases of the same version.
See full description: https://peps.python.org/pep-0440/

src/wireviz/__init__.py

@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # Please don't import anything in this file to avoid issues when it is imported in setup.py
 
-__version__ = "0.4-dev-refactored"
+__version__ = "0.4-dev251"
 
 CMD_NAME = "wireviz"  # Lower case command and module name
 APP_NAME = "WireViz"  # Application name in texts meant to be human readable