Use symbol instead of Symbol

[cprecioso]

As the TypeScript Handbook says:

Don’t ever use the types Number, String, Boolean, Symbol, or Object These types refer to non-primitive boxed objects that are almost never used appropriately in JavaScript code.
Do use the types number, string, boolean, and symbol.

Unless there is a specific reason to use Symbol, we should probably use symbol. Just checking because we are copying these types into our framework, and flagged this in our review: wasp-lang/wasp#2672 (comment)