fixed code smell

Author: sugan0tech

vertical-slice-architecture/src/test/java/com/iluwatar/verticalslicearchitecture/customer/CustomerTest.java

@@ -7,7 +7,7 @@
 class CustomerTest {
 
   @Test
-  public void testCustomerEntity() {
+  void testCustomerEntity() {
     // Arrange
     Integer id = 1;
     String name = "John Doe";