Consider upstreaming deprecation of & from LSU fork

I noticed that @alphalambda removed the `&` operator from their standard library, in favor of `pictures` (renamed to `combined` in that fork). I've had similar thoughts, and I wonder if I ought to do the same thing (slowly, with a VERY long deprecation cycle) in my own copy.

I think the issue is that students find `&` to be too much like English, and not enough like a mathematical operator. That leads them to have incorrect expectations that it can be used in all places where they want multiple things. I've seen students try to use `&` to separate animations, items in a list, and so on.

I definitely haven't decided to do this. I think I'll wait to discuss with @alphalambda after it's been used there for a while. It would be a shame to do such a disruptive deprecation, only to learn that it doesn't help! Just creating the issue to capture discussion and track the decision-making.

Beginne damit, die Diskussion zu diesem Issue und die referenzierte Änderung im LSU-Fork zu prüfen, und vergleiche anschließend, wie `\u0026` dort durch `pictures` oder `combined` ersetzt wurde. Für den Abschluss wäre eine endgültige Entscheidung darüber erforderlich, ob und wie CodeWorld den Operator als veraltet markieren sollte; es wurden keine Zieldateien oder Tests identifiziert.

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