Should `visibleProperty` of the Proportions graph columns be featured?

[pixelzoom]

Noticed when migrating overrides.js into code for https://github.com/phetsims/natural-selection/issues/331.

In natural-selection-overides.js:

    "naturalSelection.introScreen.view.graphs.proportionsNode.proportionsGraphNode.columns.earsColumn.visibleProperty": {
      "phetioFeatured": true
    },
    "naturalSelection.introScreen.view.graphs.proportionsNode.proportionsGraphNode.columns.furColumn.visibleProperty": {
      "phetioFeatured": true
    },
    "naturalSelection.introScreen.view.graphs.proportionsNode.proportionsGraphNode.columns.teethColumn.visibleProperty": {
      "phetioFeatured": true
    },
    "naturalSelection.labScreen.view.graphs.proportionsNode.proportionsGraphNode.columns.earsColumn.visibleProperty": {
      "phetioFeatured": true
    },
    "naturalSelection.labScreen.view.graphs.proportionsNode.proportionsGraphNode.columns.furColumn.visibleProperty": {
      "phetioFeatured": true
    },
    "naturalSelection.labScreen.view.graphs.proportionsNode.proportionsGraphNode.columns.teethColumn.visibleProperty": {
      "phetioFeatured": true
    },

This features the visibleProperty of each column in the Proportions graph:

But the visibleProperty is also phetioReadOnly: true, and cannot be controlled by the user. Recall that the visibility of gene-related UI components is controlled by the Properties under view.genes, for example:

So do we really want to feature something that the user can't change? I recommend that we unfeature these elements.

[pixelzoom]

Note to self: This is now featured in code. To un-feature, go to ProportionsGraphNode.ts, and delete phetioFeatured: true from inner class Column.

[amanda-phet]

Discussed with @pixelzoom and again, can't understand why I featured this, so we agreed it should be un-featured.

[pixelzoom]

Done in the above commits. proportionsGraphNode.columns.*Column.visibleProperty is now phetioFeatured: false throughout.