CLI arguments `--fixture-graph-output-type` and `--fixture-graph-output-dir` broken

[lukasjuhrich]

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Bug

When running pytest --fixture-graph --fixture-graph-output-type=svg tests, I get the following output:

ERROR: usage: pytest [options] [file_or_dir] [file_or_dir] [...]
pytest: error: argument --fixture-graph-output-type: ignored explicit argument 'svg'

Reason

Both arguments are implemented as boolean flags due to being marked as action="store_true":

https://github.com/pytest-dev/pytest-fixture-tools/blob/49d2ee71a7546c507347258239bb29afbc49ad11/pytest_fixture_tools/plugin.py#L39-L44

That should be omitted. Introduced in a232b7c9e7724725abfb890de904deef38f3722d.