unittest.mock doc: Fix references to recursive seal of Mocks (GH-9028)

The docs in `library/unittest.mock` have been updated to remove
confusing terms about submock and be explicit about the behavior
expected.
diff --git a/Doc/library/unittest.mock.rst b/Doc/library/unittest.mock.rst
index edafca0..136804c 100644
--- a/Doc/library/unittest.mock.rst
+++ b/Doc/library/unittest.mock.rst
@@ -2410,17 +2410,18 @@
 
 .. function:: seal(mock)
 
-    Seal will disable the creation of mock children by preventing getting or setting
-    of any new attribute on the sealed mock. The sealing process is performed recursively.
+    Seal will disable the automatic creation of mocks when accessing an attribute of
+    the mock being sealed or any of its attributes that are already mocks recursively.
 
-    If a mock instance is assigned to an attribute instead of being dynamically created
+    If a mock instance with a name or a spec is assigned to an attribute
     it won't be considered in the sealing chain. This allows one to prevent seal from
     fixing part of the mock object. ::
 
         >>> mock = Mock()
         >>> mock.submock.attribute1 = 2
-        >>> mock.not_submock = mock.Mock()
+        >>> mock.not_submock = mock.Mock(name="sample_name")
         >>> seal(mock)
+        >>> mock.new_attribute  # This will raise AttributeError.
         >>> mock.submock.attribute2  # This will raise AttributeError.
         >>> mock.not_submock.attribute2  # This won't raise.