Include kunit.py command in the documentation

To test that KUnit environment is setup and configured correctly
we should run "./tools/testing/kunit/kunit.py run" command. This
change adds the missing "run" part.

Google-Bug-Id: 122898129
Change-Id: I4ade52d24d08cb67fdd3cecbaeb22dd2dc11e3ca
Signed-off-by: Mike Krinkin <krinkin@google.com>
diff --git a/Documentation/test/start.rst b/Documentation/test/start.rst
index 03c3e99..c34bb88 100644
--- a/Documentation/test/start.rst
+++ b/Documentation/test/start.rst
@@ -19,7 +19,7 @@
 
 .. code-block:: bash
 
-	 ./tools/testing/kunit/kunit.py
+	 ./tools/testing/kunit/kunit.py run
 
 Creating a kunitconfig
 ======================