fix: cargo clippy warnings

error: unneeded `return` statement with `?` operator
  --> src/backup.rs:49:9
   |
49 |         return Err(APIError::InvalidBackupPath)?;
   |         ^^^^^^^ help: remove it
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_return_with_question_mark
   = note: `-D clippy::needless-return-with-question-mark` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::needless_return_with_question_mark)]`

error: could not compile `rgb-lightning-node` (bin "rgb-lightning-node") due to previous error
warning: build failed, waiting for other jobs to finish...
error: the borrowed expression implements the required traits
  --> src/test/backup_and_restore.rs:62:33
   |
62 |     let ignores = RegexSet::new(&[r"log*"]).unwrap();
   |                                 ^^^^^^^^^^ help: change this to: `[r"log*"]`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrows_for_generic_args
   = note: `-D clippy::needless-borrows-for-generic-args` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::needless_borrows_for_generic_args)]`

error: call to `.clone()` on a reference in this situation does nothing
   --> src/test/mod.rs:117:42
    |
117 |     std::fs::create_dir_all(node_test_dir.clone()).unwrap();
    |                                          ^^^^^^^^ help: remove this redundant call
    |
    = note: the type `str` does not implement `Clone`, so calling `clone` on `&str` copies the reference, which does not do anything and can be removed
    = note: `-D noop-method-call` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(noop_method_call)]`

error: could not compile `rgb-lightning-node` (bin "rgb-lightning-node" test) due to 3 previous errors
RGB-Tools / rgb-lightning-node

fix: cargo clippy warnings #3
