Put the minlen condition back in quicksort

It was accidentally removed in PR chapel-lang#15239.

---
Signed-off-by: Michael Ferguson <mppf@users.noreply.github.com>

modules/packages/Sort.chpl

@@ -1238,7 +1238,7 @@ module QuickSort {
           mid = lo + (hi-lo+1)/2;
     var piv = mid;
 
-    if hi - lo < 0 { // minlen {
+    if hi - lo < minlen {
       // base case -- use insertion sort
       InsertionSort.insertionSortMoveElts(Data, comparator=comparator, lo, hi);
       return;