Rollup merge of #113698 - compiler-errors:rpitit-check, r=spastorino

Make it clearer that we're just checking for an RPITIT

Tiny nit to use `is_impl_trait_in_trait` more, to make it clearer that we're just checking whether a def-id is an RPITIT, rather than doing something meaningful with the `opt_rpitit_info`.

r? `@spastorino`

compiler/rustc_hir_analysis/src/check/mod.rs

@@ -188,7 +188,7 @@ fn missing_items_err(
     full_impl_span: Span,
 ) {
     let missing_items =
-        missing_items.iter().filter(|trait_item| trait_item.opt_rpitit_info.is_none());
+        missing_items.iter().filter(|trait_item| !trait_item.is_impl_trait_in_trait());
 
     let missing_items_msg = missing_items
         .clone()