Log Message:
databases/ruby-sequel: update to 5.26.0

Update ruby-sequel to 5.26.0.

=== 5.26.0 (2019-11-01)

* Recognize two additional foreign key constraint violation codes on MySQL \ 
8.0.13+ (rianmcguire) (#1657)

* Support table aliases for single-table INSERT statements on PostgreSQL 9.5+ \ 
(jeremyevans) (#1656)

* Implement Sequel::Postgres::PGRange#hash so instances work correctly in hashes \ 
(jeremyevans) (#1648)

* Make dirty plugin work correctly with typecast_on_load plugin (jeremyevans) (#1647)

* Add support for :require_modification option when setting up nested_attributes \ 
(jeremyevans)

* Add support for SQL/JSON path expressions to the pg_json_ops extension, \ 
supported by PostgreSQL 12+ (jeremyevans)