Increase sleepTimeMS in allow_partial_results_with_maxTimeMS_failpoints.js to ensure that not all documents are returned from a specific shard. Currently the sleep time is calculated as Math.round(1.1 * ampleTimeMS), which is too close to ampleTimeMS. Experiments show that reducing the factor to 0.8 guarantees the test to fail, and this is pretty close to 1.1.

This task will increase the time that a shard is blocked waiting to 1.5 * ampleTimeMS.