Treat only '=' as an ini delimiter

By default both `:` and `=` are treated as delimiters by ConfigParser, but NetworkManager only treats `=` as a delimiter and uses `:` in key names.

nm2nix.py

@@ -8,7 +8,7 @@
 
 print("{")
 for i in nmfiles:
-    config = configparser.ConfigParser()
+    config = configparser.ConfigParser(delimiters=('=', ))
     config.read(i)
     connection_name = i.strip(".nmconnection")
     print(f"  {connection_name} = {{")