make the hybrid variant the default polonius algorithm

compiler/rustc_mir/src/borrow_check/nll.rs

@@ -282,7 +282,7 @@ pub(in crate::borrow_check) fn compute_regions<'cx, 'tcx>(
 
         if infcx.tcx.sess.opts.debugging_opts.polonius {
             let algorithm =
-                env::var("POLONIUS_ALGORITHM").unwrap_or_else(|_| String::from("Naive"));
+                env::var("POLONIUS_ALGORITHM").unwrap_or_else(|_| String::from("Hybrid"));
             let algorithm = Algorithm::from_str(&algorithm).unwrap();
             debug!("compute_regions: using polonius algorithm {:?}", algorithm);
             let _prof_timer = infcx.tcx.prof.generic_activity("polonius_analysis");