verifier: elide explicit lifetime

verifier: elide explicit lifetime

Fixes the clippy lint:

```
warning: the following explicit lifetimes could be elided: 'msg
  --> src/helpers/verifier.rs:93:32
   |
93 | pub(crate) fn verify_signature<'msg>(
   |                                ^^^^
94 |     msg: &'msg [u8],
   |           ^^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_lifetimes
   = note: `#[warn(clippy::needless_lifetimes)]` on by default
help: elide the lifetimes
   |
93 ~ pub(crate) fn verify_signature(
94 ~     msg: &[u8],
   |
```

Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>