This breaks the circular dependency between debhelper and dh-strip-nondeterminism.
Closes: #939720
Please see https://bugs.debian.org/939720 for more information.
The upper limit (<< 12.6~) in the alternate dependency on debhelper is only a safety guard for the case that debhelper removes its dependency on libdebhelper-perl, which is not going to happen anytime soon. So if it bothers you, feel free to remove it.