Fix calculating tsvector on hidden records

We introduced this bug in commit 55d339572, since we didn't take hidden
records into consideration.

I've tried to use `update_column` to simplify the code, but got a syntax
error `unnamed portal parameter` and didn't find how to fix it.

app/models/concerns/search_cache.rb

@@ -6,7 +6,7 @@ module SearchCache
   end
 
   def calculate_tsvector
-    self.class.where(id: id).update_all("tsv = (#{searchable_values_sql})")
+    self.class.with_hidden.where(id: id).update_all("tsv = (#{searchable_values_sql})")
   end
 
   private