Remove unused properties from the `Shadings`-implementations in `src/core/pattern.js`
Remove unused properties from the `Shadings`-implementations in `src/core/pattern.js`

Neither the `type` or the `cs` properties are used outside of the "constructors", and we can thus remove them.[1]
Note that a lot of this code is very old, and that it actually predates the main/worker-thread split before which the *same* file was used on both the main- *and* worker-threads.

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[1] On the main-thread, a similar `type` property was removed in PR 12591.

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