[gnome-todo] flatpak: Don't build the libportal docs

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit e128140d08c1faadc21ba42b81eefd451092f162
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Mon Jan 3 09:11:30 2022 +0100

    flatpak: Don't build the libportal docs
    
    This avoids useless work and fixes the build as gi-docgen is missing.

 build-aux/flatpak/org.gnome.Todo.json | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/build-aux/flatpak/org.gnome.Todo.json b/build-aux/flatpak/org.gnome.Todo.json
index 44b83d66..ff3bd23c 100644
--- a/build-aux/flatpak/org.gnome.Todo.json
+++ b/build-aux/flatpak/org.gnome.Todo.json
@@ -144,7 +144,8 @@
             "name" : "libportal",
             "buildsystem" : "meson",
             "config-opts" : [
-                "-Dbackends=gtk4"
+                "-Dbackends=gtk4",
+                "-Ddocs=false"
             ],
             "sources" : [
                 {