Remove unnecessary export, which happens to break MSVC DLL builds.

Change-Id: I47c9211274cefd26bde6bd93aa7503e022df4357
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2042874
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Bill Ticehurst <billti@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#66179}

src/heap/memory-measurement.h

@@ -19,7 +19,7 @@ namespace internal {
 class Heap;
 class NativeContextStats;
 
-class V8_EXPORT_PRIVATE MemoryMeasurement {
+class MemoryMeasurement {
  public:
   explicit MemoryMeasurement(Isolate* isolate);