Documentation/tools/rv: fix document header

align header of document with filename and rest of the content
Signed-off-by: Jiri Kastner <cz172638@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240626203906.191841-1-cz172638@gmail.com

Documentation/tools/rv/rv-mon.rst

 .. SPDX-License-Identifier: GPL-2.0
 
-=======
-rv-list
-=======
+======
+rv-mon
+======
 -----------------------
 List available monitors
 -----------------------