Squiz/LowercaseClassKeywords: improve enum tests

Let's also test the implements keyword when used with an enum.

Author: jrfnl

src/Standards/Squiz/Tests/Classes/LowercaseClassKeywordsUnitTest.inc

@@ -3,7 +3,7 @@ Abstract Class MyClass Extends MyClass {}
 Final Class MyClass Implements MyInterface {}
 Interface MyInterface {}
 Trait MyTrait {}
-Enum MyEnum {}
+Enum MyEnum IMPLEMENTS Colorful {}
 
 class MyClass
 {

src/Standards/Squiz/Tests/Classes/LowercaseClassKeywordsUnitTest.inc.fixed

@@ -3,7 +3,7 @@ abstract class MyClass extends MyClass {}
 final class MyClass implements MyInterface {}
 interface MyInterface {}
 trait MyTrait {}
-enum MyEnum {}
+enum MyEnum implements Colorful {}
 
 class MyClass
 {

src/Standards/Squiz/Tests/Classes/LowercaseClassKeywordsUnitTest.php

@@ -30,7 +30,7 @@ public function getErrorList()
             3  => 3,
             4  => 1,
             5  => 1,
-            6  => 1,
+            6  => 2,
             10 => 1,
             11 => 1,
             14 => 1,