[Code completion] Fix InObjCSelectorExprRAII destructor from f5cb115

Author: jtbandes

include/swift/Parse/CodeCompletionCallbacks.h

@@ -110,7 +110,7 @@ class CodeCompletionCallbacks {
         Callbacks->InObjCSelectorExpr = true;
     }
 
-    InObjCSelectorExprRAII() {
+    ~InObjCSelectorExprRAII() {
       if (Callbacks)
         Callbacks->InObjCSelectorExpr = false;
     }