refactor(tvix/store): drop FUSE multithread workaround for Darwin

The underlying issue in macFUSE has been fixed in
https://github.com/osxfuse/osxfuse/issues/974.

Bump our `macfuse` in nixpkgs to a version containing the fix.

This can be removed while our nixpkgs pin is bumped past
https://github.com/NixOS/nixpkgs/pull/320197.

Change-Id: Ia0e644fb13198e45018b0a218647ef211acf4df1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11824
Tested-by: BuildkiteCI
Reviewed-by: Brian Olsen <me@griff.name>

tvix/store/src/bin/tvix-store.rs

@@ -185,19 +185,12 @@ enum Commands {
     },
 }
 
-#[cfg(all(feature = "fuse", not(target_os = "macos")))]
+#[cfg(feature = "fuse")]
 fn default_threads() -> usize {
     std::thread::available_parallelism()
         .map(|threads| threads.into())
         .unwrap_or(4)
 }
-// On MacFUSE only a single channel will receive ENODEV when the file system is
-// unmounted and so all the other channels will block forever.
-// See https://github.com/osxfuse/osxfuse/issues/974
-#[cfg(all(feature = "fuse", target_os = "macos"))]
-fn default_threads() -> usize {
-    1
-}
 
 #[instrument(fields(indicatif.pb_show=1), skip(cli))]
 async fn run_cli(cli: Cli) -> Result<(), Box<dyn std::error::Error>> {