Remove unused includes from default-platform.h

It looks like the usages of these were removed in Commit
8a1bafaf ("Reland "[platform] Implement
TaskRunners in the DefaultPlatform").

Change-Id: I61865548020b6dc0ee7d658080ad148c7ffd6e42
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2187500Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67680}

src/libplatform/default-platform.h

@@ -5,11 +5,8 @@
 #ifndef V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
 #define V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
 
-#include <functional>
 #include <map>
 #include <memory>
-#include <queue>
-#include <vector>
 
 #include "include/libplatform/libplatform-export.h"
 #include "include/libplatform/libplatform.h"