Make 'nuxeo.ldap.group.mapping.label' a required field within LDAP setup wizard

When configuring the platform with LDAP Groups, the nuxeo.ldap.group.mapping.label property appears to actually be required. The startup wizard allows this field to be optional. The 'required' class should be added

Without the field set, the filter erroneously produced is:

'(&(&(&(|(objectClass=groupOfUniqueNames)(objectClass=groupOfURLs)))(cn=*))(={0}*))'

The filter (once the property is set) is:

'(&(&(&(|(objectClass=groupOfUniqueNames)(objectClass=groupOfURLs)))(cn=*))(cn={0}*))'

https://github.com/nuxeo/nuxeo/blob/10.1-SNAPSHOT/nuxeo-distribution/nuxeo-startup-wizard/src/main/webapp/userSettings.jsp#L416