[Cleanup] Delete deprecated ObjectTemplate::NewInstance() API

BUG=v8:7294,v8:8562

Change-Id: I1ed3b6d6a2fed2aee224e22ae8db5d76a52998a5
Reviewed-on: https://chromium-review.googlesource.com/c/1449731Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59301}

include/v8.h

@@ -6232,7 +6232,6 @@ class V8_EXPORT ObjectTemplate : public Template {
                                                  size_t index);
 
   /** Creates a new instance of this template.*/
-  V8_DEPRECATED("Use maybe version", Local<Object> NewInstance());
   V8_WARN_UNUSED_RESULT MaybeLocal<Object> NewInstance(Local<Context> context);
 
   /**

src/api.cc

@@ -6233,14 +6233,6 @@ MaybeLocal<v8::Object> ObjectTemplate::NewInstance(Local<Context> context) {
   RETURN_ESCAPED(result);
 }
 
-
-Local<v8::Object> ObjectTemplate::NewInstance() {
-  Local<Context> context =
-      reinterpret_cast<v8::Isolate*>(Utils::OpenHandle(this)->GetIsolate())
-          ->GetCurrentContext();
-  RETURN_TO_LOCAL_UNCHECKED(NewInstance(context), Object);
-}
-
 void v8::ObjectTemplate::CheckCast(Data* that) {
   i::Handle<i::Object> obj = Utils::OpenHandle(that);
   Utils::ApiCheck(obj->IsObjectTemplateInfo(), "v8::ObjectTemplate::Cast",