Instrument Net::LDAP::Connection#bind

Missed this but `Net::LDAP::Connection#bind` is called directly immediately after instantiating a new `Net::LDAP::Connection` object, so `Net::LDAP#bind` is never called and no instrumentation happens for this event. For example: https://github.com/ruby-ldap/ruby-net-ldap/blob/f0a95143331cf103ddd711de1697f3047f922479/lib/net/ldap.rb#L651-L653.