Fix program_id to be a pubkey instead of a string

[guibescos]

In two places of the code set_minimum_publishers is being called program_id being a string instead of a Publickey.
This made other changes I wanted to make break.

I don't know how or if python can catch these type mismatchs.

[thmzlt]

If you install the pylance and python VS code extensions, and start VS Code with poetry run code . from the project directory, it should detect type mismatches.

Also, we should eventually define a type for the instruction output.