Fix a unit test which was broken by the previous commit

This test was expecting Tor to find and use routerinfos, but hadn't
cleared the UseMicrodescriptors flag.  Part of the fix for 25213.

src/test/test_hs_service.c

@@ -1237,6 +1237,10 @@ test_build_update_descriptors(void *arg)
     node->is_running = node->is_valid = node->is_fast = node->is_stable = 1;
   }
 
+  /* We have to set thise, or the lack of microdescriptors for these
+   * nodes will make them unusable. */
+  get_options_mutable()->UseMicrodescriptors = 0;
+
   /* We expect to pick only one intro point from the node above. */
   setup_full_capture_of_logs(LOG_INFO);
   update_all_descriptors(now);