MDL-43135 Guest Enrol: new language string for with key icon

AMOS BEGIN
CPY [pluginname,enrol_guest], [guestaccess_withpassword,enrol_guest]
CPY [pluginname,enrol_guest], [guestaccess_withoutpassword,enrol_guest]
AMOS END
MDL-43135 Lang: removed redundant opentoguests