Delete fastparse2.py (#13251)

We don't need it anymore as mypy now fails unconditionally if Python 2 version is selected.

Ref #12237

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

mypy/fastparse.py

@@ -1821,15 +1821,6 @@ def note(self, msg: str, line: int, column: int) -> None:
  def translate_expr_list(self, l: Sequence[ast3.expr]) -> List[Type]:
  return [self.visit(e) for e in l]
 
- def visit_raw_str(self, s: str) -> Type:
- # An escape hatch that allows the AST walker in fastparse2 to
- # directly hook into the Python 3 type converter in some cases
- # without needing to create an intermediary `Str` object.
- _, typ = parse_type_comment(
- s.strip(), self.line, -1, self.errors, self.assume_str_is_unicode
- )
- return typ or AnyType(TypeOfAny.from_error)
-
  def visit_Call(self, e: Call) -> Type:
  # Parse the arg constructor
  f = e.func