[BUG] _commit never disposed

I was browsing the repo source and happened to notice this block. It appears that the intent was to check for and dispose the "_commit" field, not to re-check the "_begin" field. Looks like a classic copy/paste bug.

https://github.com/reactiveui/Akavache/blob/main/src/Akavache.Sqlite3/Queues/OperationQueue.cs#L375-L378

It appears that the _commit will not be disposed.