build: Declare gio-unix-2.0 dep where necessary
The launcher-box and ticket-box plugin meson files didn't declare a dependency on gio-unix-2.0
.
This can cause the build to fail with an error like:
../plugins/launcher-box/launcher-row.h:12:10: fatal error: gio/gdesktopappinfo.h: No such file or directory
12 | #include <gio/gdesktopappinfo.h>
| ^~~~~~~~~~~~~~~~~~~~~~~