fix(specs): optionalFilters additional explanation [skip-bc] (#4353)

Co-authored-by: shortcuts <[email protected]>

specs/common/schemas/SearchParams.yml

@@ -484,6 +484,7 @@ optionalFilters:
 
     - Optional filters don't work on virtual replicas.
     - Optional filters are applied _after_ sort-by attributes.
+    - Optional filters are applied _before_ custom ranking attributes (in the default [ranking](https://www.algolia.com/doc/guides/managing-results/relevance-overview/in-depth/ranking-criteria/)).
     - Optional filters don't work with numeric attributes.
 
   example: ['category:Book', 'author:John Doe']