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/engine.rs

@@ -108,7 +108,7 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
         param_env: ty::ParamEnv<'tcx>,
         value: T,
     ) -> T {
-        let infer_ok = self.infcx.at(&cause, param_env).normalize(value);
+        let infer_ok = self.infcx.at(cause, param_env).normalize(value);
         self.register_infer_ok_obligations(infer_ok)
     }
 
@@ -204,7 +204,7 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
         generic_param_scope: LocalDefId,
         outlives_env: &OutlivesEnvironment<'tcx>,
     ) -> Result<(), ErrorGuaranteed> {
-        let errors = self.infcx.resolve_regions(&outlives_env);
+        let errors = self.infcx.resolve_regions(outlives_env);
         if errors.is_empty() {
             Ok(())
         } else {