Use explicit code-block directives to disable syntax highlighting

Doc/library/pdb.rst

@@ -602,14 +602,18 @@ can be overridden by the local file.
 
    Execute the (one-line) *statement* in the context of the current stack frame.
    The exclamation point can be omitted unless the first word of the statement
-   resembles a debugger command, e.g.::
+   resembles a debugger command, e.g.:
+
+.. code-block:: none
 
       (Pdb) !next(some_iterator)
       42
       (Pdb)
 
    To set a global variable, you can prefix the assignment command with a
-   :keyword:`global` statement on the same line, e.g.::
+   :keyword:`global` statement on the same line, e.g.:
+
+.. code-block:: none
 
       (Pdb) global list_options; list_options = ['-l']
       (Pdb)