use unnamed variable for ignored exception

Author: ThoSap

src/main/java/it/aboutbits/springboot/toolbox/swagger/customization/nested_structure/NestedStructuresCustomizer.java

@@ -27,7 +27,7 @@ public void customise(OpenAPI openApi) {
                                     true
                             ));
                         }
-                    } catch (ClassNotFoundException ignored) {
+                    } catch (ClassNotFoundException _) {
                         // do nothing
                     }
                 }