Update toolbar.html

update link to https

Author: markvantilburg

demos/controlgroup/toolbar.html

@@ -271,7 +271,7 @@
 <div class="demo-description">
 	<p>A sample editor toolbar</p>
 	<p>Highlight text and edit it using the buttons and dropdowns in the toolbar.</p>
-	<p class="warning">Remember: This is only a demo and shouldn't be used for anything in production. Use a proper editor like <a href="http://prosemirror.net/">ProseMirror</a> instead.
+	<p class="warning">Remember: This is only a demo and shouldn't be used for anything in production. Use a proper editor like <a href="https://prosemirror.net/">ProseMirror</a> instead.
 </div>
 </body>
 </html>