Summary: To conform with the Ubuntu standard use metadata::trusted instead of metadata::trust. This patch must be applied after any upstream version changes since they refuse to conform. This fixes bug https://bugs.launchpad.net/bugs/1813687 Phab task T180
Test Plan: Launch trusted executable desktop files.
Reviewers: wxl, tsimonq2
Reviewed By: wxl
Differential Revision: https://phab.lubuntu.me/D54