docs: add indentation to mat-form-field with suffix example (#22502)

(cherry picked from commit 45f8566)

Author: AlexElin

src/components-examples/material/form-field/form-field-prefix-suffix/form-field-prefix-suffix-example.html

@@ -3,7 +3,7 @@
     <mat-label>Enter your password</mat-label>
     <input matInput [type]="hide ? 'password' : 'text'">
     <button mat-icon-button matSuffix (click)="hide = !hide" [attr.aria-label]="'Hide password'" [attr.aria-pressed]="hide">
-    <mat-icon>{{hide ? 'visibility_off' : 'visibility'}}</mat-icon>
+      <mat-icon>{{hide ? 'visibility_off' : 'visibility'}}</mat-icon>
     </button>
   </mat-form-field>