Remove unused variables in start command

Author: Morten N.O. Henriksen

packages/react-scripts/scripts/start.js

@@ -101,19 +101,12 @@ checkBrowsers(paths.appPath, isInteractive)
     const appName = require(paths.appPackageJson).name;
 
     const useTypeScript = fs.existsSync(paths.appTsConfig);
-    const tscCompileOnError = process.env.TSC_COMPILE_ON_ERROR === 'true';
     const urls = prepareUrls(
       protocol,
       HOST,
       port,
       paths.publicUrlOrPath.slice(0, -1)
     );
-    const devSocket = {
-      warnings: warnings =>
-        devServer.sockWrite(devServer.sockets, 'warnings', warnings),
-      errors: errors =>
-        devServer.sockWrite(devServer.sockets, 'errors', errors),
-    };
     // Create a webpack compiler that is configured with custom messages.
     const compiler = createCompiler({
       appName,