tests/avocado: Re-enable gdbsim-r5f562n8 testing U-Boot

tests/avocado: Re-enable gdbsim-r5f562n8 testing U-Boot

We disabled all RX tests on commit 9b45cc9931 ("docs/devel:
rationalise unstable gitlab tests under FLAKY_TESTS") for
being flaky. However I don't recall the U-Boot test to fail
(the problematic line checking the 'version' string is already
commented out), and I'm running this test reliably, so re-enable
it.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Yoshinori Sato <ysato@users.sourceforge.jp>
Message-Id: <20240801172332.65701-1-philmd@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240813202329.1237572-2-alex.bennee@linaro.org>