The test case for #91 is wrong

In src/12-optimizations/91-cpu-caches/cache-line/main.go, sum2 will run add operation len(s)/2 times, sum8 will run len(s)/8 times. However in src/12-optimizations/91-cpu-caches/cache-line/main_test.go, the 2 test cases set len(s) to 1_000_000. In this case, the execution counts for the two tests are different, so a fair comparison is impossible.