Update include path to date.h which was moved in the meanwhile

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:950851
Change-Id: Ia5e547e7cd7947f91814cb24de3dcf3b822905da
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1611811Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61552}

test/unittests/date-cache-unittest.cc

 // Copyright 2019 the V8 project 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 "src/base/platform/platform.h"
-#include "src/date.h"
+
+#include "src/date/date.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "unicode/strenum.h"
 #include "unicode/timezone.h"