Correct the docstring

Author: johnslavik

Lib/functools.py

@@ -889,7 +889,7 @@ def _find_impl(cls, registry):
     return registry.get(match)
 
 def _get_positional_param(func, *, pos=0):
-    """Finds the first user-specified parameter of a callable at position *pos*.
+    """Finds the first positional user-specified parameter of a callable at position *pos*.
 
     Used by singledispatch for registration by type annotation.
     *pos* should either be 0 (for functions and staticmethods) or 1 (for methods).