style(@schematics/angular): fix typo and English in environment.ts (#12023)

Author: bedag-moo

packages/schematics/angular/application/files/src/environments/environment.ts

@@ -1,15 +1,16 @@
 // This file can be replaced during build by using the `fileReplacements` array.
-// `ng build ---prod` replaces `environment.ts` with `environment.prod.ts`.
+// `ng build --prod` replaces `environment.ts` with `environment.prod.ts`.
 // The list of file replacements can be found in `angular.json`.
 
 export const environment = {
   production: false
 };
 
 /*
- * In development mode, for easier debugging, you can ignore zone related error
- * stack frames such as `zone.run`/`zoneDelegate.invokeTask` by importing the
- * below file. Don't forget to comment it out in production mode
- * because it will have a performance impact when errors are thrown
+ * For easier debugging in development mode, you can import the following file
+ * to ignore zone related error stack frames such as `zone.run`, `zoneDelegate.invokeTask`.
+ *
+ * This import should be commented out in production mode because it will have a negative impact
+ * on performance if an error is thrown.
  */
 // import 'zone.js/dist/zone-error';  // Included with Angular CLI.