docs: updated the deprecated tags in the html (#27236)

(cherry picked from commit bc7b038)

Author: alkavats1

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

@@ -275,7 +275,7 @@ <h4>Textarea</h4>
       <mat-form-field>
         <input matInput>
         <mat-label>
-          I <mat-icon>favorite</mat-icon> <b>bold</b> label
+          I <mat-icon>favorite</mat-icon> <strong>bold</strong> label
         </mat-label>
         <mat-hint>
           I also <mat-icon>home</mat-icon> <em>italic</em> hint labels

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

@@ -37,7 +37,7 @@
         <td mat-cell *matCellDef="let item">{{ item.index }}</td>
         <td mat-footer-cell *matFooterCellDef>
           <ng-container *ngIf="allSamples.length">
-            <b>Average render time</b>
+            <strong>Average render time</strong>
           </ng-container>
           <ng-container *ngIf="!allSamples.length"> No data yet </ng-container>
         </td>
@@ -47,7 +47,7 @@
         <th mat-header-cell *matHeaderCellDef>Time</th>
         <td mat-cell *matCellDef="let item">{{ item.time }}</td>
         <td mat-footer-cell *matFooterCellDef>
-          <b>{{ computedResults }}</b>
+          <strong>{{ computedResults }}</strong>
         </td>
       </ng-container>