Deduplicate 2d.filter.*.dropShadow.exceptions test statements

In filters.yaml, the same @unroll statement was present twice in a
row, probably the result of a copy-paste error.

Bug: 330885075
Change-Id: I34d770aac51ac0d9da3427c15496c32aa63346cc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5392260


Commit-Queue: Jean-Philippe Gravel <jpgravel@chromium.org>
Reviewed-by: Andres Ricardo Perez <andresrperez@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1282151}