Remove expired ports:
2020-01-01 databases/couchdb: No longer supported upstream, move to databases/couchdb2
2020-01-01 databases/riak: No longer supported upstream, see riak 2.9.0 and newer
2020-01-01 lang/erlang-runtime15: No longer supported upstream, use lang/erlang >= 21
2020-01-01 lang/erlang-runtime16: No longer supported upstream, use lang/erlang >=21
2020-01-01 lang/erlang-runtime17: No longer supported upstream, use lang/erlang >=21
2020-01-01 lang/erlang-runtime18: No longer supported upstream, use lang/erlang >=21
2020-01-01 lang/erlang-runtime19: No longer supported upstream, use lang/erlang >=21