Document #886's fix in CHANGELOG (Unreleased)

The Unreleased section didn't mention #886 (Move lazy loading from Base to
ConnectionAdapters::ConnectionHandler), which fixes adapter-specific import
support never loading for a connection established via connects_to instead
of ActiveRecord::Base.establish_connection directly - notably a Rails
multi-database secondary connection (e.g. a secondary MySQL connection),
where the previous Base-only hook never fired at all.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>