deps: V8: backport f89e555

Original commit message:

    [api] Fix compilation issue with macOS

    Fixes the following error caught by the Node.js CI:

    ../deps/v8/src/api.cc:8943:10:
      error: no viable conversion from returned value of type
      'unique_ptr<v8::internal::MicrotaskQueue, default_delete<v8::internal::MicrotaskQueue>>'
      to function return type
      'unique_ptr<v8::MicrotaskQueue, default_delete<v8::MicrotaskQueue>>'

      return microtask_queue;
             ^~~~~~~~~~~~~~~

    Change-Id: Ic09dab46bb8f87a2b3b59f5836e0883bfe0e9681
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1627533
    Commit-Queue: Michaël Zasso <mic.besace@gmail.com>
    Commit-Queue: Yang Guo <yangguo@chromium.org>
    Reviewed-by: Yang Guo <yangguo@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#61789}

Refs: v8/v8@f89e555

Backport-PR-URL: #28005
PR-URL: #27375
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

common.gypi

@@ -38,7 +38,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.5',
+    'v8_embedder_string': '-node.6',
 
     ##### V8 defaults for Node.js #####
 

deps/v8/src/api.cc

@@ -8940,7 +8940,8 @@ std::unique_ptr<MicrotaskQueue> MicrotaskQueue::New(Isolate* isolate,
   auto microtask_queue =
       i::MicrotaskQueue::New(reinterpret_cast<i::Isolate*>(isolate));
   microtask_queue->set_microtasks_policy(policy);
-  return microtask_queue;
+  std::unique_ptr<MicrotaskQueue> ret(std::move(microtask_queue));
+  return ret;
 }
 
 MicrotasksScope::MicrotasksScope(Isolate* isolate, MicrotasksScope::Type type)