Fix unnecessary console warnings when using smooth() on P2D Graphics objects

[zeesworth]

Changes:

Changed smooth implementation to match noSmooth.
Previously smooth would call setAttributes regardless of whether or not the renderer is P2D or WebGL, on Graphics objects (to my knowledge, maybe on others too) when the renderer is P2D, this would cause unnecessary logs complaining about setAttributes's use.
I have changed the smooth function to call setAttributes only if the renderer is WebGL.

I have not tested this extensively (I have though tested this change on one of my own projects using p5.js in which it functions perfectly fine),
but for such a minor change that takes from existing code I feel that it should work fine in all scenarios.
However feel free to close this pull request if there is a specific reason that the smooth function must be programmed this way

PR Checklist

• npm run lint passes
• [Inline documentation] is included / updated
• [Unit tests] are included / updated

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[davepagurek]

Looks great, thanks!