bpo-30535: [doc] state that sys.meta_path is not empty by default (GH-94098) (GH-94100)

Co-authored-by: Windson yang <wiwindson@outlook.com>
(cherry picked from commit 6575841)

Co-authored-by: Irit Katriel <1055913+iritkatriel@users.noreply.github.com>

Co-authored-by: Irit Katriel <1055913+iritkatriel@users.noreply.github.com>

Author: miss-islington

Doc/library/sys.rst

@@ -1041,7 +1041,8 @@ always available.
 
     A list of :term:`meta path finder` objects that have their
     :meth:`~importlib.abc.MetaPathFinder.find_spec` methods called to see if one
-    of the objects can find the module to be imported. The
+    of the objects can find the module to be imported. By default, it holds entries
+    that implement Python's default import semantics. The
     :meth:`~importlib.abc.MetaPathFinder.find_spec` method is called with at
     least the absolute name of the module being imported. If the module to be
     imported is contained in a package, then the parent package's :attr:`__path__`