changed 2 to 1 in 'if' pseudocode quicksort

slides/cours_7.md

@@ -140,7 +140,7 @@ int low, high; // les indices min/max des tableaux à trier
 
 ```C
 void quicksort(array, low, high) {
-    if (more than 2 elems) {
+    if (more than 1 elems) {
         pivot_ind = partition(array, low, high);
         if (something left of pivot)
             quicksort(array, low, pivot_ind - 1);