Remove "when: manual" to always build images
A few last merges to the master
branch were successful but didn't trigger container builds and subsequent image publishing.
This is bad because:
- we may miss some bugs (e.g., building fails and we don't even know about it)
- releases (image publishing) depend on manual operations, which looks fragile too.
Building in branches is also needed – to test building itself always.
In addition to this change, we need some testing, I think – but this can be solved in a separate MR.