fix(deps): remove prohibited type-ignore suppression from pyyaml security step definitions

Remove ``# type: ignore[import-untyped]`` comments from features/steps/pyyaml_security_steps.py, replacing them with proper .pyi stubs for behave.runner.Context in typings/behave/runner.pyi.

Refs: #9055

typings/behave/runner.pyi

@@ -0,0 +1,10 @@
+"""Stub for ``behave.runner`` — provides ``Context`` class used in BDD step definitions."""
+
+from typing import Any
+
+
+class Context:
+    """Behave scenario context object."""
+
+    def __init__(self) -> None: ...
+    def add_cleanup(self, func: Any, *args: Any, **kwargs: Any) -> None: ...