Revert "[C++] Add hack to not use __make_integer_seq in fatal/type/sequence library"

Summary:
This reverts commit 7e3f8ffc84980ea5bcb4dae63a1588c07460c946.
Workaround is no longer needed since new clang we use has fix for this:
https://llvm.org/bugs/show_bug.cgi?id=28519

Reviewed By: dulmarod

Differential Revision: D3791083

fbshipit-source-id: ec339f1

infer/models/cpp/include/fatal/type/sequence.h

@@ -1,23 +0,0 @@
-/*
- * Copyright (c) 2016 - present Facebook, Inc.
- * All rights reserved.
- *
- * This source code is licensed under the BSD style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
- */
-
-// TODO (t12194697) remove this file once clang in infer is updated
-// Due to bug in clang, ASTExporter is unable to mangle type of
-// __make_integer_seq bug report (fixed in clang's trunk):
-// https://llvm.org/bugs/show_bug.cgi?id=28519
-// Code that triggers the problem comes from fatal library:
-// https://github.com/facebook/fatal/blob/b53547365245219f56d4c8395b8f9410da8705a3/fatal/type/sequence.h#L874
-// We can't change value of FATAL_IMPL_HAS_MAKE_INTEGER_SEQ directly
-// instead trick header to think that it's older clang and
-// __make_integer_seq doesn't exist
-#pragma push_macro("__clang_minor__")
-#undef __clang_minor__
-#define __clang_minor__ 7
-#include_next <fatal/type/sequence.h>
-#pragma pop_macro("__clang_minor__")