Clean up redundant child_ns_entries borrows

NamespaceEntries::children returns an iterator of (&Ident, &NamespaceEntries)
so these child_ns_entries are already borrows.
diff --git a/gen/src/write.rs b/gen/src/write.rs
index 4549c21..6ee6ad7 100644
--- a/gen/src/write.rs
+++ b/gen/src/write.rs
@@ -62,7 +62,7 @@
 
     for (child_ns, child_ns_entries) in ns_entries.children() {
         writeln!(out, "namespace {} {{", child_ns);
-        gen_namespace_forward_declarations(out, &child_ns_entries);
+        gen_namespace_forward_declarations(out, child_ns_entries);
         writeln!(out, "}} // namespace {}", child_ns);
     }
 }
@@ -143,7 +143,7 @@
 
     for (child_ns, child_ns_entries) in ns_entries.children() {
         writeln!(out, "namespace {} {{", child_ns);
-        gen_namespace_contents(out, &child_ns_entries, opt);
+        gen_namespace_contents(out, child_ns_entries, opt);
         writeln!(out, "}} // namespace {}", child_ns);
     }
 }