Change the log level of the message reporting the selected Polonius algorithm to debug.

src/librustc_mir/borrow_check/nll/mod.rs

@@ -161,7 +161,7 @@ pub(in borrow_check) fn compute_regions<'cx, 'gcx, 'tcx>(
             let algorithm = env::var("POLONIUS_ALGORITHM")
                 .unwrap_or(String::from("DatafrogOpt"));
             let algorithm = Algorithm::from_str(&algorithm).unwrap();
-            info!("Using Polonius algorithm: {:?}", algorithm);
+            debug!("compute_regions: using polonius algorithm {:?}", algorithm);
             Some(Rc::new(Output::compute(
                 &all_facts,
                 algorithm,