[libc++] Temporary hack: disable Apple back-deployment testing

Apple back-deployment testing is currently failing because Green Dragon
is down. To avoid stalling the whole CI pipeline because of that, I am
temporarily disabling those jobs until Green Dragon is back, or even
better we have found a different way to store those small artifacts.

GitOrigin-RevId: 460953ad9ab5a09d77a53f0af632818bbe62e450
1 file changed