Scope clear_search_records to the account being destroyed (#2847)

Account::Searchable#clear_search_records called
Search::Record.for(id).destroy_all which deleted every row in the
shard's table, wiping search records belonging to every other account
that happened to hash to the same shard.

ref: https://3.basecamp.com/2914079/buckets/27/card_tables/cards/9782824728

app/models/account/searchable.rb

@@ -9,6 +9,6 @@ module Account::Searchable
 
   private
     def clear_search_records
-      Search::Record.for(id).destroy_all
+      Search::Record.for(id).where(account_id: id).destroy_all
     end
 end