Fix incorrect escape in Checker assertion in test 660-checker-simd-sad.

Checker was seemingly fine with these when run with Python 2, but they
are tripping it when run with Python 3.

Test: art/test/testrunner/testrunner.py --host --64 --optimizing \
        -t 660-checker-simd-sad
Bug: 170308859
Change-Id: I4e2c121008717d4b1aab59f8b4c3048a2cdc95c2
1 file changed