rustdoc: Remove some unnecessary cache parameters

Based on
https://github.com/rust-lang/rust/pull/80883#issuecomment-774437832.
The `tcx` parameters do seem to be used though, so I only removed the
`cache` parameters.

src/librustdoc/formats/cache.rs

@@ -303,7 +303,7 @@ impl<'a, 'tcx> DocFolder for CacheBuilder<'a, 'tcx> {
                             desc,
                             parent,
                             parent_idx: None,
-                            search_type: get_index_search_type(&item, self.tcx, self.cache),
+                            search_type: get_index_search_type(&item, self.tcx),
                             aliases: item.attrs.get_doc_aliases(),
                         });
                     }