test: make exported method static

The exported method can be static as it will never be called directly.

PR-URL: https://github.com/nodejs/node/pull/29102
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/addons/hello-world/binding.cc

@@ -1,7 +1,7 @@
 #include <node.h>
 #include <v8.h>
 
-void Method(const v8::FunctionCallbackInfo<v8::Value>& args) {
+static void Method(const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();
   args.GetReturnValue().Set(v8::String::NewFromUtf8(
         isolate, "world", v8::NewStringType::kNormal).ToLocalChecked());