Update AtomicLongBenchmark.java

There is a lot of clutter in this one.
 1. `@Scope.Benchmark` was redundant since you were already using `static`
 2. There is no reason to wrap `@GMB` method into `@State` if it does not reference the data.
Merge pull request #1 from shipilev/patch-1

Update AtomicLongBenchmark.java