docs(common): use <em> instead of <i> in examples (#44648)

Updated the html tag format from <i> to <em> in ts file. <em> tag helps to improve the code quality

PR Close #44648

aio/content/examples/architecture/src/app/hero-list.component.html

@@ -1,7 +1,7 @@
 <!-- #docregion -->
 <h2>Hero List</h2>
 
-<p><i>Select a hero from the list to see details.</i></p>
+<p><em>Select a hero from the list to see details.</em></p>
 <ul>
   <li *ngFor="let hero of heroes" (click)="selectHero(hero)">
     {{hero.name}}

aio/content/examples/architecture/src/app/sales-tax.component.ts

@@ -7,7 +7,7 @@ import { TaxRateService } from './tax-rate.service';
   selector:    'app-sales-tax',
   template: `
     <h2>Sales Tax Calculator</h2>
-    <p><i>Enter a number and press enter to calculate tax.</i></p>
+    <p><em>Enter a number and press enter to calculate tax.</em></p>
     <label for="amount-input">Amount: </label>
     <input type="text" id="amount-input" #amountBox (change)="0">
     <div *ngIf="amountBox.value">