Reconsider G1 default GCTimeRatio value

In JDK-8238687 G1 will make committed heap more or less follow the GCTimeRatio. Which means that there may be throughput regressions due to keeping a smaller heap now.

Further in the last few years, pauses have been optimized a lot, now taking significantly less time.

So it is natural to think about rebalancing the GCTimeRatio default value decision made years ago.