Optimize the list export SQL query
Optimize the list export SQL query

Query from the SentencesSentencesLists table to avoid one unnecessary join,
and to properly make use of indexes on that table.

Refs #1609.

Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2