Clean up 9cc1e2c1 changes to enum

This corrects a potential ABI compat problem noted by Martin Gräßlin
(cherry picked from commit 77041d785d)

kwin/lib/kdecoration.h

@@ -97,10 +97,10 @@ public:
         LowerOp,
         FullScreenOp,
         NoBorderOp,
-	ShadowOp,
         NoOp,
         SetupWindowShortcutOp,
-        ApplicationRulesOp     ///< @since 3.5
+        ApplicationRulesOp,    ///< @since 3.5
+        ShadowOp               ///< @since 3.5.12
         };
     /**
      * Basic color types that should be recognized by all decoration styles.