[mlir] Remove the unused source file.

[hokein]

Summary

It seems to be a missing file in 84d07d021333f7b5716f0444d5c09105557272e0

[Groverkss]

Included this change in the original revision since I had to revert things because of a compilation issue with gcc8 anyway.

mlir/unittests/Dialect/Affine/Analysis/AffineStructuresParser.cpp

-//===- AffineStructuresParser.cpp - Parser for AffineStructures -*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#include "./AffineStructuresParser.h"
-#include "mlir/AsmParser/AsmParser.h"
-#include "mlir/IR/IntegerSet.h"
-
-using namespace mlir;
-using namespace presburger;
-
-FailureOr<IntegerPolyhedron>
-mlir::parseIntegerSetToFAC(llvm::StringRef str, MLIRContext *context,
-                           bool printDiagnosticInfo) {
-  IntegerSet set = parseIntegerSet(str, context, printDiagnosticInfo);
-
-  if (!set)
-    return failure();
-
-  return FlatAffineValueConstraints(set);
-}