Do not generate `dco-merge-queue.yml` for private repos

[daniel-zullo-frequenz]

What's needed?

Merge queues might not be available for private repos where an enterprise plan is needed

Proposed solution

dco-merge-queue.yml should not be generated for private repos if merge queues are not available

Use cases

No response

Alternatives and workarounds

No response

Additional context

No response

[llucax]

I would like to add more options to how to generate the templates to enabled/disable features individually, like use_merge_queues or support_arm, then we could have a predefined set of defaults per type of repo (lib, actor, etc.) and repo visibility (private, public). But it is a dream, not sure if I will ever have enough time to do it :D

[llucax]

I was thinking of fixing this, but then having the file doesn't really hurt if merge queues are not used. I see a trade-off here. If we keep it, if we ever get merge queues support, everything will just work with no further updates, at the expense of having spurious files for repos that don't use merge queues.

Any opinions?