Revert "remove comment about where customization stops"

This reverts commit 7e21628.

Author: adqm

Doc/tools/static/search_scorer.js

@@ -16,6 +16,8 @@ var Scorer = {
     return score;
   },
 
+  // all values below this line are the Sphinx defaults
+
   // Additive scores depending on the priority of the object
   // Priority is set by object domains
   // (see https://www.sphinx-doc.org/en/master/extdev/domainapi.html)