Bump indexmap

`swap` has been deprecated in favour of `swap_remove` - the behaviour
is the same though.

compiler/rustc_hir_analysis/src/astconv/object_safety.rs

@@ -218,7 +218,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         for def_ids in associated_types.values_mut() {
             for (projection_bound, span) in &projection_bounds {
                 let def_id = projection_bound.projection_def_id();
-                def_ids.remove(&def_id);
+                // FIXME(#120456) - is `swap_remove` correct?
+                def_ids.swap_remove(&def_id);
                 if tcx.generics_require_sized_self(def_id) {
                     tcx.emit_node_span_lint(
                         UNUSED_ASSOCIATED_TYPE_BOUNDS,