[frontend] Rails 5.2: Update database rake task

The supports_migrations? method got deprecated in Rails 5.1 and now got
removed.
Since OBS only supports the MySQL adapter and we know that this one
supports migration dumps, we don't need this check anyway.

See rails/rails#28172 for details.

src/api/lib/tasks/databases.rake

@@ -48,9 +48,7 @@ namespace :db do
         raise "Task not supported by '#{abcs[Rails.env]['adapter']}'"
       end
 
-      if ActiveRecord::Base.connection.supports_migrations?
-        structure << ActiveRecord::Base.connection.dump_schema_information
-      end
+      structure << ActiveRecord::Base.connection.dump_schema_information
 
       structure.gsub!(%r{AUTO_INCREMENT=[0-9]* }, '')
       structure.gsub!('auto_increment', 'AUTO_INCREMENT')