Updated a code block to use the emphasize-lines Sphinx option

docs/howto/legacy-databases.txt

@@ -57,13 +57,14 @@ Python declaration of each one of these models to specify it is a
 :attr:`managed <django.db.models.Options.managed>` one. For example, consider
 this generated model definition:
 
-.. parsed-literal::
+.. code-block:: python
+    :emphasize-lines: 5
 
     class Person(models.Model):
         id = models.IntegerField(primary_key=True)
         first_name = models.CharField(max_length=70)
         class Meta:
-            **managed = False**
+           managed = False
            db_table = 'CENSUS_PERSONS'
 
 If you wanted to modify existing data on your ``CENSUS_PERSONS`` SQL table