fix a couple of clippy warnings:

filter_next
manual_strip
redundant_static_lifetimes
single_char_pattern
unnecessary_cast
unused_unit
op_ref
redundant_closure
useless_conversion

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -739,7 +739,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 "cannot infer {} {} {} `{}`{}",
                 kind_str, preposition, descr, type_name, parent_desc
             )
-            .into()
         }
     }
 }