The one in bionic-proposed is however dead anyhow as its binaries failed to upload. So:
Removing packages from bionic-proposed: postgresql-9.6 9.6.6-0ubuntu1 in bionic
Comment: Clashed with postgresql-10 and failed to upload
1 package successfully removed.
Actually there is a postgresql-9.6 in bionic release pocket:
postgresql-9.6 | 9.6.5-1 | bionic | source, amd64, arm64, armhf, i386, ppc64el, s390x
The one in bionic-proposed is however dead anyhow as its binaries failed to upload. So:
Removing packages from bionic-proposed:
postgresql- 9.6 9.6.6-0ubuntu1 in bionic
Comment: Clashed with postgresql-10 and failed to upload
1 package successfully removed.