[sqlite] create_collation: memory leak

[gwenn]

https://github.com/launchbadge/sqlx/blob/master/sqlx-core/src/sqlite/connection/collation.rs#L59

https://sqlite.org/c3ref/create_collation.html

The xDestroy callback is not called if the sqlite3_create_collation_v2() function fails. Applications that invoke sqlite3_create_collation_v2() with a non-NULL xDestroy argument should check the return code and dispose of the application data pointer themselves rather than expecting SQLite to deal with it for them.

See rusqlite fix.