fix: resolve spotbugs exception softening violation

Author: anshullakra007

src/main/java/com/thealgorithms/sorts/ConcurrentMergeSort.java

@@ -93,7 +93,7 @@ private static void concurrentMergeSort(int[] array, int[] temp, int left, int r
             leftTask.get();
         } catch (InterruptedException | ExecutionException e) {
             Thread.currentThread().interrupt();
-            throw new RuntimeException("Concurrent execution interrupted or failed", e);
+            throw new IllegalStateException("Concurrent execution interrupted or failed", e);
         }
 
         merge(array, temp, left, mid, right);

src/test/java/com/thealgorithms/sorts/ConcurrentMergeSortTest.java

@@ -97,7 +97,7 @@ public void testInterruptedException() {
         Thread.currentThread().interrupt();
         try {
             ConcurrentMergeSort.sort(array);
-        } catch (RuntimeException e) {
+        } catch (IllegalStateException e) {
             org.junit.jupiter.api.Assertions.assertTrue(e.getCause() instanceof InterruptedException || e.getCause() instanceof java.util.concurrent.ExecutionException, "Should catch and wrap InterruptedException or ExecutionException");
         } finally {
             // Clear interrupted status so it doesn't affect subsequent tests