[Config] Document the 'replication.anon' option

**Product:** Tarantool
**Since:** 3.0
**Root document:** https://github.com/tarantool/doc/issues/3664
**SME:** @ totktonada

# Details

Old content: https://www.tarantool.io/en/doc/latest/reference/configuration/#cfg-replication-replication-anon
