src: remove unused function

PR-URL: https://github.com/nodejs/node/pull/9243
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

src/inspector_agent.cc

@@ -170,13 +170,6 @@ std::string GenerateID() {
            buffer[7]);
   return uuid;
 }
-
-// std::to_string is not available on Smart OS and ARM flavours
-const std::string to_string(uint64_t number) {
-  std::ostringstream result;
-  result << number;
-  return result.str();
-}
 }  // namespace