updates reform gem

Updates reform to profit from now [fully qualified modules](https://github.com/apotonick/reform/commit/bf236ffc9fd5725126489e5aa5709e0f7f6d0985).

This fixes incompatibilities with reporting_engine's Widget::Controls::Save class.

Thanks goes to @myabc for this.

Fixes: https://www.openproject.org/work_packages/13838