MAINTAINERS: Fix F: in "Build and test automation"

We neglected to update MAINTAINERS when we split off the testing docs. Commit 97b091c88f (MAINTAINERS: Update the paths to the testing documentation files, 2025-06-10) updated it belatedly, but missed one line. Correct that now. Fixes: ff41da5030 (docs/devel: Split testing docs from the build docs and move to separate folder, 2024-08-30) Cc: Alex Bennée <alex.bennee@linaro.org> Cc: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com> Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com> Message-ID: <20260603064032.3733394-37-armbru@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@mailo.com>