clean up unused feature

I merged !41 (merged) forgetting we did not have a CI like Duniter's which checks things like:

warning: unexpected `cfg` condition value: `dev`
 --> src/commands/transfer.rs:3:11
  |
3 | #[cfg(any(feature = "dev", feature = "gdev"))] // find how to get runtime calls
  |           ^^^^^^^^^^-----
  |                     |
  |                     help: there is a expected value with a similar name: `"gdev"`
  |