GTasks: Google tasks not shown in scheduled list

## What Happened

Tasks with due date from the Google backend are not shown in the scheduled list. This has two potential solutions:

1. The EDS version used is [only capable to query for `has-start?`](https://github.com/elementary/tasks/issues/149). The `has-due?` s-expression is not yet available ([will be in EDS 3.39.1+](https://gitlab.gnome.org/GNOME/evolution-data-server/-/issues/254))
2. EDS converts tasks from `GData.TasksTask` to `ICal.Component` and does not set the start date in this conversion

Solving either of these problems would allow to show GTasks in the scheduled list. But in both cases a newer EDS release is needed. Therefore the first solution would be preferred and may be achievable by bundling a newer EDS version within Flatpak.

## Expected Behavior

All tasks with due date should be shown in the scheduled list - incl. GTasks.