refactor: ensure all 'TODO's are consistent (#23252)

PR Close #23252

aio/content/examples/dependency-injection-in-action/src/app/hero-of-the-month.component.1.ts

@@ -8,7 +8,7 @@ import { MinimalLogger }       from './minimal-logger.service';
 @Component({
   selector: 'app-hero-of-the-month',
   templateUrl: './hero-of-the-month.component.html',
-  // Todo: move this aliasing, `useExisting` provider to the AppModule
+  // TODO: move this aliasing, `useExisting` provider to the AppModule
   providers: [{ provide: MinimalLogger, useExisting: LoggerService }]
 })
 export class HeroOfTheMonthComponent {

aio/content/examples/dependency-injection-in-action/src/app/hero.service.ts

@@ -5,7 +5,7 @@ import { Hero }       from './hero';
 @Injectable()
 export class HeroService {
 
-  // TODO move to database
+  // TODO: move to database
   private heroes: Array<Hero> = [
     new Hero(1, 'RubberMan', 'Hero of many talents', '123-456-7899'),
     new Hero(2, 'Magma', 'Hero of all trades', '555-555-5555'),

aio/content/examples/dependency-injection-in-action/src/app/parent-finder.component.ts

@@ -151,7 +151,7 @@ export class BethComponent implements Parent {
 // #docregion alex-1
 })
 // #enddocregion alex-1
-// Todo: Add `... implements Parent` to class signature
+// TODO: Add `... implements Parent` to class signature
 // #docregion alex-1
 // #docregion alex-class-signature
 export class AlexComponent extends Base