gh-148588: Drop 'optional' from __lazy_modules__ iterable description

Author: johnslavik

Doc/reference/datamodel.rst

@@ -1124,7 +1124,7 @@ the following writable attributes:
 
 .. attribute:: module.__lazy_modules__
 
-   An optional :term:`iterable` of fully qualified module name strings.  When defined
+   An :term:`iterable` of fully qualified module name strings.  When defined
    at module scope, any regular :keyword:`import` statement in that module whose
    target module name appears in this iterable is treated as a
    :ref:`lazy import <lazy-imports>`, as if the :keyword:`lazy` keyword had