chore(skills): remove NoteType::from(felt!(2)) workaround after compiler fix

## Context

The rust-sdk-pitfalls skill currently documents that P2ID output notes created in contract code must use `NoteType::from(felt!(2))` instead of `NoteType::Private`. This is because `NoteType::Private` doesn't exist in the current compiler SDK, which is a bug in the compiler.

This workaround was added as part of the Miden Day feedback fixes (project-template#28).

## When to action

Once the compiler SDK exposes `NoteType::Private` as a proper enum variant (matching the host-side API), update the pitfalls skill to remove the `NoteType::from(felt!(2))` workaround and replace it with `NoteType::Private`.

Depends on the compiler fix being shipped.