community/syncthing: upgrade to 1.15.1
includes fix for CVE-2021-21404
security advisory: https://github.com/syncthing/syncthing/security/advisories/GHSA-x462-89pf-6r5h
includes fix for CVE-2021-21404
security advisory: https://github.com/syncthing/syncthing/security/advisories/GHSA-x462-89pf-6r5h