Update pattern matching docs for changes to the PEP (#25185)

See:
- https://github.com/python/peps/pull/1909 (__match_args__ must be a tuple)
- https://github.com/python/peps/pull/1908 (allow keyword patterns for int(x) etc.)
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index dfe5eb6..9c819b7 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -2565,7 +2565,7 @@
 
 .. data:: object.__match_args__
 
-   This class variable can be assigned a tuple or list of strings. When this class is
+   This class variable can be assigned a tuple of strings. When this class is
    used in a class pattern with positional arguments, each positional argument will
    be converted into a keyword argument, using the corresponding value in
    *__match_args__* as the keyword. The absence of this attribute is equivalent to