Documentation: kunit: fixed sphinx error in code block

Fix a missing newline in a code block that was causing a warning:

Documentation/dev-tools/kunit/usage.rst:553: WARNING: Error in "code-block" directive:
maximum 1 argument(s) allowed, 3 supplied.

.. code-block:: bash
        modprobe example-test

Signed-off-by: Brendan Higgins <[email protected]>
Reviewed-by: Alan Maguire <[email protected]>
Signed-off-by: Shuah Khan <[email protected]>

Author: bjh83

Documentation/dev-tools/kunit/usage.rst

@@ -551,6 +551,7 @@ options to your ``.config``:
 Once the kernel is built and installed, a simple
 
 .. code-block:: bash
+
 	modprobe example-test
 
 ...will run the tests.