function plt_hide_mailin_menus() {
//Hide "Brevo".
remove_menu_page('sib_page_home');
//Hide "Brevo → Home".
remove_submenu_page('sib_page_home', 'sib_page_home');
//Hide "Brevo → Forms".
remove_submenu_page('sib_page_home', 'sib_page_form');
//Hide "Brevo → Statistics".
remove_submenu_page('sib_page_home', 'sib_page_statistics');
}
add_action('admin_menu', 'plt_hide_mailin_menus', 10000);