List the olimex-stm32-h405 board in the document title, so that the
board name appears in the table of contents in system/target-arm.rst.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Message-id: 20241018141332.942844-2-peter.maydell@linaro.org