pearsonSpearmanCov: Reuse existing allocator

Author: Geod24

source/dstats/cor.d

@@ -1225,7 +1225,6 @@ private void pearsonSpearmanCov(bool makeNewMatrix, RoR, Matrix)
             break;
         case CorCovType.spearman:
             foreach(row; pool.parallel(normalized)) {
-                auto alloc = newRegionAllocator();
                 auto buf = alloc.uninitializedArray!(double[])(row.length);
                 rank(row, buf);