Revert "refactor: disable esbuild worker threads"

This reverts commit 47a1ccc.

Author: alan-agius4

packages/angular_devkit/build_angular/src/webpack/plugins/javascript-optimizer-plugin.ts

@@ -168,12 +168,6 @@ export class JavaScriptOptimizerPlugin {
           const workerPool = new Piscina({
             filename: workerPath,
             maxThreads: MAX_OPTIMIZE_WORKERS,
-            env: {
-              ...process.env,
-              // Workaround for `TypeError [Error]: Cannot read property 'workerPort' of undefined`
-              // See: https://github.com/evanw/esbuild/commit/aa8b9ce8d462378f0f06ac52e83f6c32332dde38
-              ESBUILD_WORKER_THREADS: '0',
-            },
           });
 
           // Enqueue script optimization tasks and update compilation assets as the tasks complete