plots wizard: indentation issue

[dberenbaum]

When I used the Add a plot functionality, I ended up with an invalid dvc.yaml due to wrong indentation:

Screen.Recording.2023-12-14.at.3.54.19.PM.mov

[julieg18]

Our yaml library doesn't work with list items that have an indentation level of 0. I think I can add a solution that checks for this and updates the yaml text manually. Will be a little hacky though :)