[clang][AST] Remove unnecessary 'const'.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@363585 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/AST/Expr.h b/include/clang/AST/Expr.h
index d66f2e8..508817f 100644
--- a/include/clang/AST/Expr.h
+++ b/include/clang/AST/Expr.h
@@ -1024,7 +1024,7 @@
     llvm_unreachable("invalid ResultKind");
   }
   ResultStorageKind getResultStorageKind() const {
-    return static_cast<const ResultStorageKind>(ConstantExprBits.ResultKind);
+    return static_cast<ResultStorageKind>(ConstantExprBits.ResultKind);
   }
   APValue getAPValueResult() const;