Fix type hints for py3.8

Author: jsa34

src/pytest_bdd/gherkin_parser.py

@@ -140,7 +140,7 @@ class GherkinDocument(BaseModel):
     comments: List[Comment]
 
 
-def _compute_given_when_then(steps: list[Step]) -> list[Step]:
+def _compute_given_when_then(steps: List[Step]) -> List[Step]:
     last_gwt = None
     for step in steps:
         if step.keyword in STEP_TYPES:

src/pytest_bdd/parser.py

@@ -338,7 +338,7 @@ def get_step_type(keyword: str) -> str | None:
             keyword (str): The keyword for the step (e.g., 'given', 'when', 'then').
 
         Returns:
-            str | None: The type of the step, or None if the keyword is unknown.
+            Optional[str]: The type of the step, or None if the keyword is unknown.
         """
         return {
             "given": GIVEN,