ci: ship sg image without deploy
Created by: jhchabran
Hotfix for a bug introduced in https://github.com/sourcegraph/sourcegraph/pull/32326#discussion_r821860229 that @bobheadxi spotted after the merge (thank you so much for reviewing it anyway!).
Test plan
- check in CI that the image is still built (https://buildkite.com/sourcegraph/sourcegraph/builds/135736)