ART: Temporarily move 704-multiply-accumulate away from D8

Postpones switching to D8 for test failing on the ART buildbots.

Failure only observed for gcstress test variants.

Bug: 65168732
Test: art/test.py --32 --target -r --gcstress -t 704
Change-Id: Iabccc4b7cb1ecc155ad972450e8995eec4b62959