This makes v8's _monkeyYaml happy --- without it, the info block never ends, and we fail to parse the `features` key.
An explicit indentation marker isn't used because monkeyYaml doesn't supported it, and adding it might slightly slow things down.
Using PyYAML instead was considered, but after trying it, I don't think it looks viable. [simple test cases](https://gist.github.com/caitp/4a59a67f671907c11051a1b7bd5fdaae)
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