net/py-s3transfer: upgrade 0.1.5 to 0.1.8

Changelog:

0.1.8

• feature:download: Support downloading to FIFOs.

0.1.7

• bugfix:TransferManager: Fix memory leak when using same client to create multiple TransferManagers

0.1.6

• bugfix:download: Fix issue where S3 Object was not downloaded to disk when empty

PR: 213353
Submitted by: Bradley T. Hughes (maintainer)
Approved by: swills (mentor)