client: Remove Pygments dependency from manpage

This patch removes the Pygments dependency from btmon .rst file.
When the code-block type is specified, the rst2man throws a warning
asking for Pygments package.

client/bluetoothctl.rst

@@ -339,7 +339,7 @@ AUTOMATION
 Two common ways to automate the tool are to use Here Docs or the program expect.
 Using Here Docs to show information about the Bluetooth controller.
 
-.. code:: bash
+.. code::
 
    bluetoothctl <<EOF
    list