Update s3.md (#9477)
Update s3.md (#9477)

Because in the preceding paragraphs we talk about creating a bucket and/or a user and there are also bucket and user policies, I thing it is important to make clear the example policy is a 'user' policy and not a bucket policy.

Added a link to AWS for information about creating a user policy.
thaJeztah/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,docker/docker.github.io