Remove --harmony-modules flag and let embedder decide when modules are used

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 26ebfa8a6775163c01e75c00d54e728fc950ecdf..71b8864d1f0245ff8e0c165b5ac231fca24429e6 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -1853,7 +1853,6 @@ Local<Script> ScriptCompiler::Compile(
 MaybeLocal<Script> ScriptCompiler::CompileModule(Local<Context> context,
                                                  Source* source,
                                                  CompileOptions options) {
-  CHECK(i::FLAG_harmony_modules);
   auto isolate = context->GetIsolate();
   TRACE_EVENT_SCOPED_CONTEXT("V8", "Isolate", isolate);
   auto maybe = CompileUnboundInternal(isolate, source, options, true);