gh-104683: Argument clinic: Make the filename parameter to Clinic…

… required (#107439)

Tools/clinic/clinic.py

@@ -2015,7 +2015,6 @@ def __post_init__(self, args: tuple[str, ...]) -> None:
  if self.type =='file':
  d = {}
  filename = self.clinic.filename
- assert filename is not None
  d['path'] = filename
  dirname, basename = os.path.split(filename)
  if not dirname:
@@ -2133,8 +2132,8 @@ def __init__(
  language: CLanguage,
  printer: BlockPrinter | None = None,
  *,
+ filename: str,
  verify: bool = True,
- filename: str | None = None
  ) -> None:
  # maps strings to Parser objects.
  # (instantiated from the "parsers" global.)