LibJS: Rename BitNot -> BitwiseNot to match other bitwise operators

Author: https://github.com/0xtechnobabble
Commit: 20a0fc5576
Pull-request: https://github.com/SerenityOS/serenity/pull/1456

Libraries/LibJS/AST.h

@@ -304,7 +304,7 @@ private:
 };
 
 enum class UnaryOp {
-    BitNot,
+    BitwiseNot,
     Not,
 };