fix(ResourceExplorer2): set endpoint to dualstack by default

[trivikr]

Internal JS-3686

Testing

import AWS from "./index";

(async () => {
  const client1 = new AWS.ResourceExplorer2({ region: "us-west-2" });
  console.log("default endpoint:", client1.config.endpoint);

  const client2 = new AWS.ResourceExplorer2({
    region: "us-west-2",
    useDualstackEndpoint: false,
  });
  console.log(
    "endpoint with useDualstackEndpoint=false:",
    client2.config.endpoint
  );

  const client3 = new AWS.ResourceExplorer2({
    region: "us-west-2",
    useDualstackEndpoint: true,
  });
  console.log(
    "endpoint with useDualstackEndpoint=true:",
    client3.config.endpoint
  );
})();

default endpoint: resource-explorer-2.us-west-2.api.aws
endpoint with useDualstackEndpoint=false: resource-explorer-2.us-west-2.api.aws
endpoint with useDualstackEndpoint=true: resource-explorer-2.us-west-2.api.aws

Checklist

• npm run test passes
• changelog is added, npm run add-change