Update release-notes.md
Update release-notes.md

Changed year to 2019 for 2.6.1 and 2.5.7. Will change the actual date on release date.
londoncalling/docker.github.io,londoncalling/docker.github.io,docker/docker.github.io,londoncalling/docker.github.io,thaJeztah/docker.github.io,londoncalling/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,londoncalling/docker.github.io,docker/docker.github.io