modals: Update checkbox in deactivate user modal to be same as others.

This commit changes the design of checkbox in deactivate user modal
to be same as others in the app. We have added parent element with
".new-style" class for now, since we have this for all other checkbox
in the app and this seems to be the simplest solution.

In future, we plan to remove the "new-style" class and instead add
CSS based on a component for checkbox elements.

web/templates/confirm_dialog/confirm_deactivate_user.hbs

@@ -18,13 +18,15 @@
         </ul>
     {{/if}}
 </p>
-<label class="checkbox">
-    <input type="checkbox" class="send_email" data-key="{{ key }}" />
-    {{#tr}}
-    Notify this user by email?
-    {{/tr}}
-    <span></span>
-</label>
+<div class="new-style">
+    <label class="checkbox">
+        <input type="checkbox" class="send_email" data-key="{{ key }}" />
+        <span></span>
+        {{#tr}}
+        Notify this user by email?
+        {{/tr}}
+    </label>
+</div>
 <div class="email_field">
     <p class="border-top">
         <strong>{{t "Subject" }}:</strong>