S3 - mat to system param typo

[seglo]

A continuation of #2513, #2494

I noticed all the Scala DSL usages of Materializer remained without an ActorSystem overload. It's not possible to add the overload without conflicts, so I made a breaking change instead.

i.e.

[error] both method deleteBucket in object S3 of type (bucketName: String, s3Headers: akka.stream.alpakka.s3.S3Headers)(implicit mat: akka.stream.Materializer, implicit attributes: akka.stream.Attributes)scala.concurrent.Future[akka.Done]
[error] and  method deleteBucket in object S3 of type (bucketName: String, s3Headers: akka.stream.alpakka.s3.S3Headers)(implicit system: akka.actor.ClassicActorSystemProvider, implicit attributes: akka.stream.Attributes)scala.concurrent.Future[akka.Done]
[error] match argument types (String,akka.stream.alpakka.s3.S3Headers) and expected result type scala.concurrent.Future[akka.Done]
[error]     deleteBucket(bucketName, S3Headers.empty)
                        

[ennru]

LGTM.

[seglo]

Mostly resolved in #2626. This just fixes a typo.