Doesn't build using the Flatpak manifest

[YaLTeR]

What should happen:

It builds and runs fine.

What happened instead:

First the GTK 4 meson dependency is >=4.3.0 whereas the runtime from the manifest (org.gnome.Platform//40) only has 4.2.1. After fixing that, I get the following error:

../../../../../../../../../source/vala/tootle/src/Dialogs/Composer/Dialog.vala:35.13-35.33: error: The type name `Adw.ViewStack' could not be found
    [GtkChild] unowned Adw.ViewStack stack;
               ^^^^^^^^^^^^^^^^^^^^^
../../../../../../../../../source/vala/tootle/src/Views/TabbedBase.vala:9.12-9.24: error: The type name `Adw.ViewStack' could not be found
    protected Adw.ViewStack stack;
              ^^^^^^^^^^^^^

How to reproduce:

1. Clone in Builder and press Run.

Build context:

• Distro: Fedora 34 Silverblue
• App version: f774eb9
• Build type: Flatpak

[bleakgrey]

Ah, right. I forgot to update the manifest.