Revert "Require V8 to be explicitly initialized before an Isolate is created"

src/d8.cc

Index: src/d8.cc
diff --git a/src/d8.cc b/src/d8.cc
index 9db77449442c7be5b5fa4ae246d607fc52baa9e1..c1d66b4d3c8e3002e72eddce659bd28f7ffd9588 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -1619,7 +1619,6 @@ int Shell::Main(int argc, char* argv[]) {
   v8::V8::InitializeICU(options.icu_data_file);
   v8::Platform* platform = v8::platform::CreateDefaultPlatform();
   v8::V8::InitializePlatform(platform);
-  v8::V8::Initialize();
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
   StartupDataHandler startup_data(options.natives_blob, options.snapshot_blob);
 #endif