cppgc: Fix the age-table unittest

Bug: chromium:1325007
Change-Id: I6adb06c4b15e5656f2b2c47b49d6a225750a6b2a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3695572
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Auto-Submit: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81067}

test/unittests/heap/cppgc/age-table-unittest.cc

@@ -19,7 +19,7 @@ class AgeTableTest : public testing::TestWithHeap {
 
   AgeTableTest()
       : disallow_gc_(GetHeapHandle()),
-        age_table_(CagedHeap::Instance().local_data().age_table) {}
+        age_table_(CagedHeapLocalData::Get().age_table) {}
 
   ~AgeTableTest() override {
     age_table_.Reset(GetPlatform().GetPageAllocator());