AV1 RT: Prune palette more for nonRD case

about 3% speed up on speed 10 for screen content.
With 0.05dB quality regression

Change-Id: I76eb6fc7c9529cfa917d8d3190e287365bbda08d
diff --git a/av1/encoder/speed_features.c b/av1/encoder/speed_features.c
index 7dbabbc..16e4c78 100644
--- a/av1/encoder/speed_features.c
+++ b/av1/encoder/speed_features.c
@@ -1330,6 +1330,7 @@
   sf->lpf_sf.disable_lr_filter = 1;
   sf->rt_sf.skip_interp_filter_search = 1;
   sf->intra_sf.prune_palette_search_level = 2;
+  sf->intra_sf.prune_luma_palette_size_search_level = 2;
 
   // End of set