The failure condition being fixed is `w1` and `w2` could belong
to different users, organizations, and templates and still cause a
serializable failure if run concurrently. This is because the old query
did a `seq scan` on the `workspace_builds` table. Since that is the
table being updated, we really want to prevent that.
So before this would fail for any 2 workspaces. Now it only fails if
`w1` and `w2` are owned by the same user and organization.
