PEP-673 use Self as return type for classmethods (#94)

* PEP-673 use Self as return type for classmethods

* add dummy test file

* remove python3.10 compat

src/ahriman/application/handlers/sign.py

@@ -30,7 +30,7 @@ class Sign(Handler):
     """
 
     @classmethod
-    def run(cls: type[Handler], args: argparse.Namespace, architecture: str, configuration: Configuration, *,
+    def run(cls, args: argparse.Namespace, architecture: str, configuration: Configuration, *,
             report: bool, unsafe: bool) -> None:
         """
         callback for command line