Lower log-level of message concerning test binaries that didn't get b…

…uilt

fix: #359

crates/cargo-maelstrom/src/cargo.rs

@@ -139,7 +139,7 @@ impl<StreamT: io::Read> GenericTestArtifactStream<StreamT> {
  if !pkg.built_tests.is_empty() {
  assert!(!pkg.unbuilt_non_test_binaries.is_empty());
  for b in &pkg.unbuilt_non_test_binaries {
- slog::warn!(
+ slog::debug!(
  self.log,
  "didn't receive build notification for {id:?} binary {b:?}"
  );