[api] Remove deprecated EmbedderHeapTracer::AbortTracing

V8 has no path in calling this API and thus there is no way for the
embedder to get notified about this event.

Bug: chromium:843903
Change-Id: I938675aed9191a292f21bae0fed0e3ea8acaf936
Reviewed-on: https://chromium-review.googlesource.com/c/1434377
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59087}

include/v8.h

@@ -7077,15 +7077,6 @@ class V8_EXPORT EmbedderHeapTracer {
    */
   virtual void EnterFinalPause(EmbedderStackState stack_state) = 0;
 
-  /**
-   * Called when tracing is aborted.
-   *
-   * The embedder is expected to throw away all intermediate data and reset to
-   * the initial state.
-   */
-  V8_DEPRECATED("Obsolete as V8 will not abort tracing anymore.",
-                virtual void AbortTracing()) {}
-
   /*
    * Called by the embedder to request immediate finalization of the currently
    * running tracing phase that has been started with TracePrologue and not

test/cctest/heap/test-embedder-tracing.cc

@@ -61,7 +61,6 @@ class TestEmbedderHeapTracer final : public v8::EmbedderHeapTracer {
 
   void TracePrologue() final {}
   void TraceEpilogue() final {}
-  void AbortTracing() final {}
   void EnterFinalPause(EmbedderStackState) final {}
 
   bool IsRegisteredFromV8(void* first_field) const {