Docs: Specify the requirement for fs.s3.impl/fs.s3a.impl configuration for remove_orphan_files procedure to work

[samredai]

The docs should specify the s3 configuration needed for remove_orphan_files to work properly (as well as the hadoop aws jars). Thanks @ajreid21 for pointing this out!

[steveloughran]

you don't have to specify fs.s3a.impl for s3a to work. that's a stack overflow/spark superstition. recommend closing as invalid