Downgrade accesskit_unix to 0.17.0

Workaround for a 0.18 regression where accessibility doesn't work under
normal conditions.

https://github.com/niri-wm/niri/issues/3594

https://github.com/AccessKit/accesskit-c/issues/76

src/a11y.rs

@@ -3,7 +3,7 @@ use std::thread;
 
 use accesskit::{
     ActionHandler, ActionRequest, ActivationHandler, DeactivationHandler, Live, Node, NodeId, Role,
-    Tree, TreeId, TreeUpdate,
+    Tree, TreeUpdate,
 };
 use accesskit_unix::Adapter;
 use calloop::LoopHandle;
@@ -220,7 +220,6 @@ impl Niri {
         let update = TreeUpdate {
             nodes,
             tree: None,
-            tree_id: TreeId::ROOT,
             focus,
         };
 
@@ -247,7 +246,6 @@ impl Niri {
         let update = TreeUpdate {
             nodes: vec![(ID_ANNOUNCEMENT, node)],
             tree: None,
-            tree_id: TreeId::ROOT,
             focus: self.a11y.focus,
         };
 
@@ -341,7 +339,6 @@ impl Niri {
                 (ID_MRU, mru),
             ],
             tree: Some(tree),
-            tree_id: TreeId::ROOT,
             focus,
         }
     }