[3.13] [docs] TypeVarTuple default is keyword-only (GH-119215) (#119224)

(cherry picked from commit e406b39)

Co-authored-by: Sebastian Rittau <srittau@rittau.biz>

Author: miss-islington

Doc/library/typing.rst

@@ -1780,7 +1780,7 @@ without the dedicated syntax, as documented below.
 
 .. _typevartuple:
 
-.. class:: TypeVarTuple(name, default=typing.NoDefault)
+.. class:: TypeVarTuple(name, *, default=typing.NoDefault)
 
    Type variable tuple. A specialized form of :ref:`type variable <typevar>`
    that enables *variadic* generics.