Fix double-encoding typo

Author: SteveSandersonMS

src/Microsoft.AspNetCore.NodeServices/Content/Node/entrypoint-http.js

@@ -83,7 +83,7 @@
  return;
  }
  res.setHeader('Content-Type', 'application/json');
- res.end(JSON.stringify(successValueJson));
+ res.end(successValueJson);
  }
  else {
  // String - can bypass JSON-serialization altogether

src/Microsoft.AspNetCore.NodeServices/TypeScript/HttpNodeInstanceEntryPoint.ts

@@ -29,7 +29,7 @@ const server = http.createServer((req, res) => {
  return;
  }
  res.setHeader('Content-Type', 'application/json');
- res.end(JSON.stringify(successValueJson));
+ res.end(successValueJson);
  } else {
  // String - can bypass JSON-serialization altogether
  res.setHeader('Content-Type', 'text/plain');