Back out "Change Context Pool Stripes from 4 to 128"

Summary:
Original commit changeset: 7b10cb9dd2c4

`configerator_proxy2` reports a big memory regression. Reverting until we understand what's going on and have a plan to address it.

(Note: this ignores all push blocking failures!)

Differential Revision: D30401909

fbshipit-source-id: 28443ba08b75c634021965319fead2f8a36b7235

folly/compression/CompressionContextPoolSingletons.h

@@ -65,13 +65,13 @@ using ZSTD_CCtx_Pool = CompressionCoreLocalContextPool<
     ZSTD_CCtx_Creator,
     ZSTD_CCtx_Deleter,
     ZSTD_CCtx_Resetter,
-    128>;
+    4>;
 using ZSTD_DCtx_Pool = CompressionCoreLocalContextPool<
     ZSTD_DCtx,
     ZSTD_DCtx_Creator,
     ZSTD_DCtx_Deleter,
     ZSTD_DCtx_Resetter,
-    128>;
+    4>;
 
 /**
  * Returns a clean ZSTD_CCtx.