Run doctest helper initializer after connection

Without this, ActiveRecord does not yet know which type of adapter to
use. This makes monkey patching the specific adapter class(es) that you
need impossible.

This mirrors what we do in the spec helper.

activerecord-ksuid/spec/doctest_helper.rb

@@ -6,11 +6,11 @@
 
 require 'active_record/ksuid/railtie'
 
-ActiveRecord::KSUID::Railtie.initializers.each(&:run)
-ActiveSupport.run_load_hooks(:active_record, ActiveRecord::Base)
-
 ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
 ActiveRecord::Base.logger = Logger.new(IO::NULL)
 ActiveRecord::Schema.verbose = false
 
+ActiveRecord::KSUID::Railtie.initializers.each(&:run)
+ActiveSupport.run_load_hooks(:active_record, ActiveRecord::Base)
+
 ActiveSupport::Deprecation.instance.silenced = true