[libfuzzer] remove icu fuzzers (moved to //third_party/icu/fuzzers).

testing/libfuzzer/fuzzers/icu_uregex_open_fuzzer.cc

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include <stddef.h>
-#include <stdint.h>
-
-#include "third_party/icu/source/i18n/unicode/regex.h"
-
-// Entry point for LibFuzzer.
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
-  UParseError pe = { 0 };
-  UErrorCode status = U_ZERO_ERROR;
-  URegularExpression* re = uregex_open(reinterpret_cast<const UChar*>(data),
-                                       static_cast<int>(size) / sizeof(UChar),
-                                       0, &pe, &status);
-  if (re)
-    uregex_close(re);
-
-  return 0;
-}