Squiz/ControlStructureSpacing: fix the enum test

The test as-it-was, wasn't actually testing anything. As the sniff is about control structures, the `enum` needs to be nested in one before the test would fail without the fix,

src/Standards/Squiz/Tests/WhiteSpace/ControlStructureSpacingUnitTest.inc

@@ -262,6 +262,8 @@ $expr = match( $foo ){
 };
 echo $expr;
 
-enum SomeEnum
-{
+if($true) {
+
+    enum SomeEnum {}
+
 }

src/Standards/Squiz/Tests/WhiteSpace/ControlStructureSpacingUnitTest.inc.fixed

@@ -254,6 +254,8 @@ $expr = match($foo){
 
 echo $expr;
 
-enum SomeEnum
-{
+if($true) {
+
+    enum SomeEnum {}
+
 }