[dev-context] CGModules update: Filter version 2021.09.05 published.

Aditya Mahajan submitted an update to the Filter package. Version number: 2021.09.05 License type: BSD License (simplified) Wants to be in ConTeXt distribution: yes Wants to be synced with CTAN: yes Summary description: A module to run external programs on the contents of start-stop evironment Announcement text: ---------------------------------------------------------------------- Bugfix release. * The inteface of \splitfilename changed due the which \externalfilterbasename was incorrect. Using the new interface now. ----------------------------------------------------------------------