Move all lms lettuce tests into shard 1

@benpatterson

Now that we have moved the lettuce acceptance tests to bok-choy, the lms lettuce shards are only taking ~2 minutes each. 

See for example: https://jenkins.testeng.edx.org/job/edx-all-tests-auto-master/1985/testReport/

So let's collapse into shard 1 and use 1 fewer worker.