[4.2.x] Refs #34140 -- Applied rst code-block to non-Python examples.

Thanks to J.V. Zammit, Paolo Melchiorre, and Mariusz Felisiak for
reviews.

Backport of 534ac48297 from main.

docs/ref/contrib/postgres/functions.txt

@@ -20,7 +20,9 @@ operation to install it.
 
 .. _pgcrypto extension: https://www.postgresql.org/docs/current/pgcrypto.html
 
-Usage example::
+Usage example:
+
+.. code-block:: pycon
 
     >>> from django.contrib.postgres.functions import RandomUUID
     >>> Article.objects.update(uuid=RandomUUID())
@@ -41,7 +43,9 @@ sets up a transaction and thus sets the time that ``TransactionNow()`` will
 return; nested calls create savepoints which do not affect the transaction
 time.
 
-Usage example::
+Usage example:
+
+.. code-block:: pycon
 
     >>> from django.contrib.postgres.functions import TransactionNow
     >>> Article.objects.filter(published__lte=TransactionNow())