Development status not set for spp_custom_filter and spp_custom_filter_ui

[kneckinator]

Ci reports that spp_base, which has the development status Production/Stable, has started to depend on a component with an undefined status as of the commit 5dcfc82

The proposed solution is to add the meta-data descriptor development_status in the __manifest__.py files of spp_custom_filter and spp_custom_filter_ui to Production/Stable.

The status Production/Stable has been confirmed by @anjclarise as no major issues have been uncovered on the QA test instances.