internal/postgres: replace "version" with "module" in some messages
internal/postgres: replace "version" with "module" in some messages

Change-Id: Icaf0ad1d0b421471c4f444b5524d323fdcc60e1c
Reviewed-on: https://team-review.git.corp.google.com/c/golang/discovery/+/727099
CI-Result: Cloud Build <ea5729d4cf3392b9d382b6ca272c65aa27554f44@system.gserviceaccount.com>
Reviewed-by: Julie Qiu <e6cb64861edcc38971590ff27c111e0e672de045@google.com>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite