fixup! Bug 40701: Add security warning when downloading a file

Bug 42641: Use moz-button-group for panel buttons.

browser/components/downloads/content/downloadsPanel.inc.xhtml

@@ -126,12 +126,12 @@
               class="downloads-tor-warning-tails-link"
             ></html:a>
           </html:p>
-          <html:div class="panel-footer">
+          <html:moz-button-group class="panel-footer">
             <html:button
-              class="downloads-tor-warning-dismiss-button"
+              class="footer-button downloads-tor-warning-dismiss-button"
               data-l10n-id="downloads-tor-warning-dismiss-button"
             ></html:button>
-          </html:div>
+          </html:moz-button-group>
         </vbox>
         <toolbarseparator />
       </vbox>