make last name optional

app/views/profile/index.html.erb

@@ -12,7 +12,7 @@
         </div>
         <div class="form-control">
           <%= f.label :last_name, t('last_name'), class: 'label' %>
-          <%= f.text_field :last_name, required: true, class: 'base-input', dir: 'auto' %>
+          <%= f.text_field :last_name, required: false, class: 'base-input', dir: 'auto' %>
         </div>
       </div>
       <div class="form-control">