Relax required test score

New test was added following bhtsne bump (which cannot now be seeded). Relaxed tolerance to make it more robust in CI

Author: relf

algorithms/linfa-tsne/src/lib.rs

@@ -138,7 +138,7 @@ mod tests {
             .perplexity(10.0)
             .transform(ds)?;
 
-        assert!(ds.silhouette_score()? > 0.5);
+        assert!(ds.silhouette_score()? > 0.4);
 
         Ok(())
     }