Remove references to recursive

[gjtempleton]

Since the switch to Drone 0.5 syntax and using S3 go SDKs rather than calling out to the AWS CLI the recursive option has actually been obsolete, this simply removes this dead code.

(The commit where this became obsolete is here: https://github.com/drone-plugins/drone-s3/commit/6c101e57efe308d4255254f1fc7e1cbb86e297f5 )

[bradrydzewski]

thanks Guy!