change to no STEP_LIMIT for ShellSort

Author: moritzfl

src/main/java/de/moritzf/sorting/logic/sorting/ShellSort.java

@@ -29,7 +29,7 @@ public class ShellSort extends SortingAlgorithm {
 
     private static final String NAME = "Shellsort";
 
-    private static final int STEP_LIMIT = 20;
+    private static final int STEP_LIMIT = -1;
 
     private ArrayList<ShellStep> protocol = new ArrayList<>();