gitlab: include new aarch32 job in custom-runners

Without linking it in it won't be presented on the UI. Also while
doing that fix the misnamed job from 20.40 to 20.04.

Fixes: cc44a160 ("gitlab: add a new aarch32 custom runner definition")
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20220315121954.2283887-1-alex.bennee@linaro.org>