Minor docstring fix

src/testcrush/grammars/transformers.py

@@ -302,6 +302,7 @@ def start(self, formulas: list[tuple[str, str]]) -> dict[str, str]:
     def formula(self, formula_name: str, formula: str) -> tuple[str, str]:
         """
         Takes the lhs and rhs and returns them as a tuple
+
         .. highlight:: python
         .. code-block:: python