fix(tester): re-apply MacOS CI fix (commit 6fde964)

Reapply 6fde964 (fix(tester): make human rule trace writer blocking,
2025-01-08)

PR #569 accidentally reverted this change, causing ACCEPT=true failures
on my Mac and some CI failures.

conjure_oxide/tests/generated_tests.rs

@@ -99,7 +99,7 @@ fn integration_test(path: &str, essence_base: &str, extension: &str) -> Result<(
     // run tests in sequence not parallel when verbose logging, to ensure the logs are ordered
     // correctly
 
-    let (subscriber, _guards) = create_scoped_subscriber(path, essence_base);
+    let subscriber = create_scoped_subscriber(path, essence_base);
 
     // set the subscriber as default
     tracing::subscriber::with_default(subscriber, || {
@@ -392,20 +392,17 @@ fn assert_constants_leq_one(parent_expr: &Expression, exprs: &[Expression]) {
 pub fn create_scoped_subscriber(
     path: &str,
     test_name: &str,
-) -> (
-    impl tracing::Subscriber + Send + Sync,
-    Vec<tracing_appender::non_blocking::WorkerGuard>,
-) {
-    let (target1_layer, guard1) = create_file_layer_json(path, test_name);
-    let (target2_layer, guard2) = create_file_layer_human(path, test_name);
-    let layered = target1_layer.and_then(target2_layer);
+) -> (impl tracing::Subscriber + Send + Sync) {
+    //let (target1_layer, guard1) = create_file_layer_json(path, test_name);
+    let target2_layer = create_file_layer_human(path, test_name);
+    let layered = target2_layer;
 
     let subscriber = Arc::new(tracing_subscriber::registry().with(layered))
         as Arc<dyn tracing::Subscriber + Send + Sync>;
     // setting this subscriber as the default
     let _default = tracing::subscriber::set_default(subscriber.clone());
 
-    (subscriber, vec![guard1, guard2])
+    subscriber
 }
 
 fn create_file_layer_json(
@@ -428,24 +425,19 @@ fn create_file_layer_json(
     (layer1, guard1)
 }
 
-fn create_file_layer_human(
-    path: &str,
-    test_name: &str,
-) -> (impl Layer<Registry> + Send + Sync, WorkerGuard) {
+fn create_file_layer_human(path: &str, test_name: &str) -> (impl Layer<Registry> + Send + Sync) {
     let file = File::create(format!("{path}/{test_name}-generated-rule-trace-human.txt"))
         .expect("Unable to create log file");
 
-    let (non_blocking, guard2) = tracing_appender::non_blocking(file);
-
     let layer2 = fmt::layer()
-        .with_writer(non_blocking)
+        .with_writer(file)
         .with_level(false)
         .without_time()
         .with_target(false)
         .with_filter(EnvFilter::new("rule_engine_human=trace"))
         .with_filter(FilterFn::new(|meta| meta.target() == "rule_engine_human"));
 
-    (layer2, guard2)
+    layer2
 }
 
 #[test]