Changes done in tests for BAEL-876 (#1843)

* Correction in first two tests

* Add new test

for RecursionWithCorrectTerminationCondition

* BAEL-876 Removed static method qualifier

core-java/src/main/java/com/baeldung/stackoverflowerror/RecursionWithCorrectTerminationCondition.java

@@ -1,7 +1,7 @@
 package com.baeldung.stackoverflowerror;
 
 public class RecursionWithCorrectTerminationCondition {
-    public static int calculateFactorial(final int number) {
+    public int calculateFactorial(final int number) {
         return number <= 1 ? 1 : number * calculateFactorial(number - 1);
     }
 }