visibleProperty should be uninstrumented instead of read-only

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For phetsims/qa#889, noticed while working on #317.

There are 7 inappropriate occurrences of this option:

visiblePropertyOptions: { phetioReadOnly: true }

This instruments visibleProperty but makes it read-only. It's only appropriate to use this when the visibility of the element can somehow be controlled via the sim, in case the client wants to inspect the value of visibleProperty. In all cases for this sim, the visibility never changes, so it would be more appropriate to uninstrument visibleProperty, like this:

phetioVisiblePropertyInstrumented: false

This will require grunt generate-phet-io-api to update the API files. @arouinfar FYI.

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Done in the above commit, and API files regenerated for both sims. There's nothing to review here, because these visibleProperty elements are now gone. So I'll go ahead and close.

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Reopening to confirm in phetsims/qa#894. It looks like changes I made during dev testing did not get into the 1.7 release branch.

@samreid @matthew-blackman FYI.

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Looks OK in 1.7. Closing.