Hiding a filter in a view with same filter in contextual filters
The following code will help you to solve your issue.

/**
 * Implement hook_form_alter().
 */
function mymodule_form_alter(&amp;$form, &amp;$form_state, $form_id) {

  if($form_id == 'views_exposed_form') {
    if($form['#id'] == 'views-exposed-form-myview-page') {
       // argument 1 represent city1 
      if(arg(1)) {
        // hide city field 
        unset($form['#info']['filter-jobs_in_city']);
        hide($form['jobs_in_city']);
      }
    }
  }
}


Notes:


Replace form id views-exposed-form-myview-page with your own form id
Replace argument 1 with the right City1 argument index 
Replace jobs_in_city field name with your own city field