rust: init: replace unwraps with question mark operators

rust: init: replace unwraps with question mark operators

Use `?` operator in the doctests. Since it is in the examples,
using unwraps can convey a wrong impression that unwrapping is
fine in general, thus this patch removes this unwrapping.

Suggested-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/rust-for-linux/CANiq72nsK1D4NuQ1U7NqMWoYjXkqQSj4QuUEL98OmFbq022Z9A@mail.gmail.com/
Signed-off-by: Daniel Sedlak <daniel@sedlak.dev>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241123095033.41240-2-daniel@sedlak.dev
[ Reworded commit slightly. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>