doc: fix heading level of itest examples

The Examples section should be on the second heading level.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/usage/cmd/itest.rst b/doc/usage/cmd/itest.rst
index 9c307fb..adcad05 100644
--- a/doc/usage/cmd/itest.rst
+++ b/doc/usage/cmd/itest.rst
@@ -58,7 +58,7 @@
     ======== ======================
 
 Examples
-========
+--------
 
 The itest command sets the result variable $? to true (0) or false (1):