Fix clippy::needless_borrow in the compiler

`x clippy compiler -Aclippy::all -Wclippy::needless_borrow --fix`.

Then I had to remove a few unnecessary parens and muts that were exposed
now.

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -252,7 +252,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
             fresh_preds.insert(self.clean_pred(infcx, predicate.as_predicate()));
         }
 
-        let mut select = SelectionContext::new(&infcx);
+        let mut select = SelectionContext::new(infcx);
 
         let mut already_visited = FxHashSet::default();
         let mut predicates = VecDeque::new();