RFR: Do not mention GC in Partial GC ops

[Roman Kennke]

> http://cr.openjdk.java.net/~shade/shenandoah/concpartial-drop-gc/webrev.01/
>
> As Christine mentions separately, having a "GC" line in logs that does not decrease heap occupancy
> might be perceived as the bug. Let us partially (pun intended) manage that by dropping "GC" from
> those lines, so that concurrent phase would look like a part of larger cycle.
>
> [13.341s][info][gc     ] GC(3) Pause Init Partial 2.229ms
> [13.363s][info][gc     ] GC(3) Concurrent partial 21420M->21556M(102400M) 21.912ms
> [13.364s][info][gc     ] GC(3) Pause Final Partial 0.914ms
> [13.373s][info][gc     ] GC(3) Concurrent cleanup 21560M->1132M(102400M) 9.714ms
>
> Testing: hotspot_gc_shenandoah
>
> Thanks,
> -Aleksey
>
Looks better indeed. Go from me!