Make decreaseValue method thread-safe by adding synchronized modifier.

Author: chertiav

src/main/java/core/basesyntax/Counter.java

@@ -12,7 +12,7 @@ public Counter(int value) {
         this.value = value;
     }
 
-    public void decreaseValue() {
+    public synchronized void decreaseValue() {
         logger.info(String.format(MESSAGE,
                 "Before decrementing", Thread.currentThread().getName(), value));
         value--;