[Sync] Fix ShouldUntrackEntity unittest

FakeModelTypeSyncBridge::Store::HasMetadata expects storage key, while
client tag hash was actually passed, so fixed expectation had no
effect.

Bug: 973409
Change-Id: I2ad835a7fc9eaa5a0bc89aaa22b39d493786d9ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1827362
Auto-Submit: Maksim Moskvitin <mmoskvitin@google.com>
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700242}

components/sync/model_impl/client_tag_based_model_type_processor_unittest.cc

@@ -2127,7 +2127,7 @@ TEST_F(ClientTagBasedModelTypeProcessorTest, ShouldUntrackEntity) {
   // Metadata should not be written under kUntrackKey1. This means that
   // UntrackEntity was called and corresponding ProcessorEntity is
   // removed and no storage key got propagated to MetadataChangeList.
-  EXPECT_FALSE(db()->HasMetadata(kHash1));
+  EXPECT_FALSE(db()->HasMetadata(kKey1));
   EXPECT_EQ(0U, db()->metadata_count());
   EXPECT_EQ(0, bridge()->get_storage_key_call_count());
 }