refactor(tvix/store): remove anyhow::Result in directory it test

There's no `?` being used.

Change-Id: Ifbfd88f6056e0064d11458cb335d05b333ec7b6b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8127
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

tvix/store/src/proto/tests/directory_nodes_iterator.rs

@@ -5,7 +5,7 @@ use crate::proto::FileNode;
 use crate::proto::SymlinkNode;
 
 #[test]
-fn iterator() -> anyhow::Result<()> {
+fn iterator() {
     let d = Directory {
         directories: vec![
             DirectoryNode {
@@ -77,6 +77,4 @@ fn iterator() -> anyhow::Result<()> {
         vec!["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l"],
         node_names
     );
-
-    Ok(())
 }