pythongh-104146: Argument clinic: remove dead code highlighted by the…

… `vulture` tool (python#107632)

Tools/clinic/clinic.py

@@ -1684,27 +1684,30 @@ class Block:
  found on the start line of the block between the square
  brackets.
 
- signatures is either list or None. If it's a list,
- it may only contain clinic.Module, clinic.Class, and
+ signatures is a list.
+ It may only contain clinic.Module, clinic.Class, and
  clinic.Function objects. At the moment it should
  contain at most one of each.
 
  output is either str or None. If str, it's the output
  from this block, with embedded '\n' characters.
 
- indent is either str or None. It's the leading whitespace
+ indent is a str. It's the leading whitespace
  that was found on every line of input. (If body_prefix is
  not empty, this is the indent *after* removing the
  body_prefix.)
 
- preindent is either str or None. It's the whitespace that
+ "indent" is different from the concept of "preindent"
+ (which is not stored as state on Block objects).
+ "preindent" is the whitespace that
  was found in front of every line of input *before* the
  "body_prefix" (see the Language object). If body_prefix
  is empty, preindent must always be empty too.
 
- To illustrate indent and preindent: Assume that '_'
- represents whitespace. If the block processed was in a
- Python file, and looked like this:
+ To illustrate the difference between "indent" and "preindent":
+
+ Assume that '_' represents whitespace.
+ If the block processed was in a Python file, and looked like this:
  ____#/*[python]
  ____#__for a in range(20):
  ____#____print(a)
@@ -1717,7 +1720,6 @@ class Block:
  signatures: list[Module | Class | Function] = dc.field(default_factory=list)
  output: Any = None # TODO: Very dynamic; probably untypeable in its current form?
  indent: str = ''
- preindent: str = ''
 
  def __repr__(self) -> str:
  dsl_name = self.dsl_name or "text"
@@ -2049,12 +2051,8 @@ def dump(self) -> str:
  return self.buffers.dump()
 
 
-# maps strings to Language objects.
-# "languages" maps the name of the language ("C", "Python").
-# "extensions" maps the file extension ("c", "py").
+# "extensions" maps the file extension ("c", "py") to Language classes.
 LangDict = dict[str, Callable[[str], Language]]
-
-languages = { 'C': CLanguage, 'Python': PythonLanguage }
 extensions: LangDict = { name: CLanguage for name in "c cc cpp cxx h hh hpp hxx".split() }
 extensions['py'] = PythonLanguage
 
@@ -4427,7 +4425,6 @@ class DSLParser:
  positional_only: bool
  group: int
  parameter_state: ParamState
- seen_positional_with_default: bool
  indent: IndentStack
  kind: FunctionKind
  coexist: bool
@@ -4458,7 +4455,6 @@ def reset(self) -> None:
  self.positional_only = False
  self.group = 0
  self.parameter_state: ParamState = ParamState.START
- self.seen_positional_with_default = False
  self.indent = IndentStack()
  self.kind = CALLABLE
  self.coexist = False