[ModelicaSystemCmd] fix mypy warning in ModelicaSystemDoE on usage of args_set()

Author: syntron

OMPython/ModelicaSystem.py

@@ -137,7 +137,7 @@ def __init__(self, runpath: pathlib.Path, modelname: str, timeout: Optional[int]
         self._args: dict[str, str | None] = {}
         self._arg_override: dict[str, str] = {}
 
-    def arg_set(self, key: str, val: Optional[str | dict] = None) -> None:
+    def arg_set(self, key: str, val: Optional[str | dict[str, Any]] = None) -> None:
         """
         Set one argument for the executable model.
 
@@ -180,7 +180,7 @@ def arg_get(self, key: str) -> Optional[str | dict]:
 
         return None
 
-    def args_set(self, args: dict[str, Optional[str | dict[str, str]]]) -> None:
+    def args_set(self, args: dict[str, Optional[str | dict[str, Any]]]) -> None:
         """
         Define arguments for the model executable.