chore(tvix/castore): remove commented-out test fixture

This became obsolete, since the introduction of a stricter `Directory`
struct invalid names cannot be represented anymore.

Change-Id: I9e4b1b6cca01831d0a9735f58d8a1f59ac18676b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12615
Reviewed-by: flokli <flokli@flokli.de>
Reviewed-by: edef <edef@edef.eu>
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

tvix/castore/src/directoryservice/directory_graph.rs

@@ -271,15 +271,7 @@ impl ValidatedDirectoryGraph {
             .filter_map(move |i| nodes[i.index()].weight.take())
     }
 }
-/*
-        pub static ref BROKEN_DIRECTORY : Directory = Directory {
-            symlinks: vec![SymlinkNode {
-                name: "".into(), // invalid name!
-                target: "doesntmatter".into(),
-            }],
-            ..Default::default()
-        };
-*/
+
 #[cfg(test)]
 mod tests {
     use crate::fixtures::{DIRECTORY_A, DIRECTORY_B, DIRECTORY_C};