Replace remote_syslog with remote_syslog2

Summary

The Omnibus GitLab makes use of remote_syslog Ruby gem, but this has been deprecated by the authors. This is replaced by a Go implementation found in remote_syslog2 by the same group.

Proposal

The remote_syslog gem has not seen code changes of any kind since June of 2015. remote_syslog2 is seeing active changes. This will be a shift, but the license remains the MIT.

Related to #6029