Adjust max refs count per group for by_refs merging strategy
Adjust max refs count per group for by_refs merging strategy

Summary: Based on the previous modifications to the grouping logic here, this is the parameter combination showing the best results.

Reviewed By: Feng23

Differential Revision: D30002980

fbshipit-source-id: c2687851e4484a139b87a7aeb7d5d852c34f540a

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex