Fix SLES gpg url
Fix SLES gpg url

The gpg key is in the top level directory for each distribution, using "${DOCKER_EE_URL}/sles/gpg" will attempt to load the gpg key from within the 12.3/<architecture>/<version>/ subdirectory, because of how DOCKER_EE_URL is set before.
anweiss/docker.github.io,londoncalling/docker.github.io,docker/docker.github.io,londoncalling/docker.github.io,anweiss/docker.github.io,docker/docker.github.io,docker/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,londoncalling/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,londoncalling/docker.github.io,londoncalling/docker.github.io,anweiss/docker.github.io,anweiss/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,anweiss/docker.github.io