wordpress remove all dashboard widgets
// Main column (left):
// Browser Update Required
$wp_meta_boxes['dashboard']['normal']['high']['dashboard_browser_nag'];
// PHP Update Required
$wp_meta_boxes['dashboard']['normal']['high']['dashboard_php_nag'];
// At a Glance
$wp_meta_boxes['dashboard']['normal']['core']['dashboard_right_now'];
// Right Now
$wp_meta_boxes['dashboard']['normal']['core']['network_dashboard_right_now'];
// Activity
$wp_meta_boxes['dashboard']['normal']['core']['dashboard_activity'];
// Site Health Status
$wp_meta_boxes['dashboard']['normal']['core']['health_check_status'];
// Side Column (right):
// WordPress Events and News
$wp_meta_boxes['dashboard']['side']['core']['dashboard_primary'];
// Quick Draft, Your Recent Drafts
$wp_meta_boxes['dashboard']['side']['core']['dashboard_quick_press'];