devel/thunar-vcs-plugin: Import upstream change fixing icon naming issue

Import an upstream change that adds a domain to icon names to avoid
conflicts with other software packages.

PR: 287804
Approved by: Sergey V. Dyatko <sergey.dyatko@gmail.com> (maintainer)
Obtained from: https://gitlab.xfce.org/thunar-plugins/thunar-vcs-plugin/-/merge_requests/22