docs(multiple): replace deprecated html tags (#27141)

(cherry picked from commit 12ec8fa)

Author: aanchal88

src/components-examples/material/chips/chips-form-control/chips-form-control-example.html

@@ -3,7 +3,7 @@
   <button mat-raised-button (click)="formControl.enable()">Enable form control</button>
 </div>
 <p>
-  <i>Enter video keywords</i>
+  <em>Enter video keywords</em>
 </p>
 <mat-form-field class="example-form-field">
   <mat-label>Video keywords</mat-label>

src/components-examples/material/dialog/dialog-overview/dialog-overview-example.html

@@ -9,6 +9,6 @@
     <button mat-raised-button (click)="openDialog()">Pick one</button>
   </li>
   <li *ngIf="animal">
-    You chose: <i>{{animal}}</i>
+    You chose: <em>{{animal}}</em>
   </li>
 </ol>

src/components-examples/material/form-field/form-field-label/form-field-label-example.html

@@ -28,7 +28,7 @@
           <mat-option>-- None --</mat-option>
           <mat-option value="option">Option</mat-option>
         </mat-select>
-        <mat-label><mat-icon>favorite</mat-icon> <b> Fancy</b> <i> label</i></mat-label>
+        <mat-label><mat-icon>favorite</mat-icon> <b> Fancy</b> <em> label</em></mat-label>
       </mat-form-field>
     </div>
   </form>

src/dev-app/input/input-demo.html

@@ -318,7 +318,7 @@ <h4>Textarea</h4>
           I <mat-icon>favorite</mat-icon> <b>bold</b> label
         </mat-label>
         <mat-hint>
-          I also <mat-icon>home</mat-icon> <i>italic</i> hint labels
+          I also <mat-icon>home</mat-icon> <em>italic</em> hint labels
         </mat-hint>
       </mat-form-field>
     </p>

src/dev-app/legacy-input/legacy-input-demo.html

@@ -278,7 +278,7 @@ <h4>Textarea</h4>
           I <mat-icon>favorite</mat-icon> <b>bold</b> label
         </mat-label>
         <mat-hint>
-          I also <mat-icon>home</mat-icon> <i>italic</i> hint labels
+          I also <mat-icon>home</mat-icon> <em>italic</em> hint labels
         </mat-hint>
       </mat-form-field>
     </p>

src/dev-app/legacy-list/legacy-list-demo.html

@@ -187,15 +187,15 @@ <h2>Line alignment</h2>
     <mat-list>
       <mat-list-item *ngFor="let link of links">
         <span mat-line>{{ link.name }}</span>
-        <span>Not in an <i>matLine</i></span>
+        <span>Not in an <em>matLine</em></span>
       </mat-list-item>
     </mat-list>
 
     <mat-selection-list>
       <mat-list-option value="first">First</mat-list-option>
       <mat-list-option value="second">
         <span matLine>Second</span>
-        <span>Not in an <i>matLine</i></span>
+        <span>Not in an <em>matLine</em></span>
       </mat-list-option>
     </mat-selection-list>
   </div>