Depend on upstream ruamel.yaml instead of unmaintained ruamel_yaml

[mbargull]

Comment:

I'm currently looking at what packages on conda-forge have a dependency on the non-maintained ruamel_yaml package.

It'd be good if we could have this package depend on ruamel.yaml instead of ruamel_yaml, too.

NB: The latest conda-forge::ruamel_yaml is still at version 0.15.80 -- upstream released that version 5 years ago.

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Faunus uses the PyYAML top-level yaml.safe_load/yaml.safe_dump functions which have been removed in ruamel.yaml=0.18 (see https://pypi.org/project/ruamel.yaml/0.18.4/ for details).
I've issued an upstream PR to use the load/dump methods from ruamel.yaml.YAML(typ="safe") for compatibility with ruamel.yaml=0.18 at mlund/faunus#435 . (Though not tested by me, due to time constraints.)

It may make sense to add an upper bound on the ruamel.yaml dependency with ,<0.19.0a0 with the upstream PR included or ,<0.18.0a0 without.

[mlund]

Closed by #47