package/cage: bump to version v0.2.0-15-g2e593fe5a
wlroots 0.19.0 includes API breaking changes.
This commit bump the cage version to include the upstream commit [1]
which updates to this new wlroots API.
[1] https://github.com/cage-kiosk/cage/commit/9ad44e4f521edf446ad66559726e6deeb8204101
Signed-off-by: Raphael Pavlidis <raphael.pavlidis@gmail.com>
[Julien: change _VERSION to use "git describe --abbrev=40" format]
Signed-off-by: Julien Olivain <ju.o@free.fr>