disable the jeepyb trivial rebase hook on review-dev.o.o

This change is for the pending gerrit upgrade.  Gerrit 2.8 has built-in trivial rebase
detection[1].  This change disables the jeepyb trivial rebase hook on review-dev.o.o so
so we can use and test gerrit's built-in rebase detector instead.

[1] https://gerrit-review.googlesource.com/Documentation/config-labels.html#label_copyAllScoresOnTrivialRebase
and https://gerrit-review.googlesource.com/Documentation/config-labels.html#label_copyAllScoresIfNoCodeChange

Closes-Bug: #1273959
Partial-Bug: #1082781

Change-Id: Ia14d8ee86b9d59b6f79ee873231bb0d13b7f43d2
Merge "disable the jeepyb trivial rebase hook on review-dev.o.o"