Update an optimization remark test for change D18777.
This test checks the loop-vectorization remarks when pointer checking threshold is exceeded. The change in D18777 would introduce zexts that cannot be removed so that the "loop not vectorized" reason is changed, hence breaking this test.
Modified the offsets to be 1 and the zexts could be finally removed by indvars (this magic fact is attributed to some scev mechanisms). Since the purpose of this test is checking the vectorization options, the offset numbers don't matter.