gh-142349: Clarify lazy import filters have positional-only parameters

Doc/library/sys.rst

@@ -1790,13 +1790,13 @@ always available. Unless explicitly noted otherwise, all variables are read-only
    callable or ``None`` to clear the filter.
 
    The filter function is called for every potentially lazy import to
-   determine whether it should actually be lazy. It must have the following
+   determine whether it should actually be lazy. It should have the following
    signature::
 
       def filter(importing_module: str, imported_module: str,
                  fromlist: tuple[str, ...] | None) -> bool
 
-   Where:
+   The function is called with three positional arguments:
 
    * *importing_module* is the name of the module doing the import
    * *imported_module* is the resolved name of the module being imported
@@ -1805,6 +1805,8 @@ always available. Unless explicitly noted otherwise, all variables are read-only
    * *fromlist* is the tuple of names being imported (for ``from ... import``
      statements), or ``None`` for regular imports
 
+   These arguments are passed positionally.
+
    The filter should return ``True`` to allow the import to be lazy, or
    ``False`` to force an eager import.