Exclude outlines from dev group

[DouweM]

These packages will be pulled in by make install anyway.

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[Kludex]

I don't see the point then... If you are working in this repo, you'll do make install anyway.

[DouweM]

@Kludex Outlines pulls in a ton of large dependencies, and every CI step was doing sync --dev, even those that didn't intend to test "all extras", just slim or standard. So this way the slim/standard envs are more realistic and smaller.