*: fix clippy issues with Rust 1.88+.

[dongsupark]

Starting from Rust 1.88, clippy prints out warnings in case of uninlined format arguments in format strings.
Fix them to unblock CI.

error: variables can be used directly in the `format!` string
Error:   --> omaha/src/response.rs:70:29
   |
70 |             _ => return Err(format!("unknown success action \"{}\"", s)),
   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
   = note: `-D clippy::uninlined-format-args` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::uninlined_format_args)]`
help: change this to
   |
70 -             _ => return Err(format!("unknown success action \"{}\"", s)),
70 +             _ => return Err(format!("unknown success action \"{s}\"")),

Fixes #70

[krnowak]

Maybe somehow disabling this lint could be the way forward, but you already did the work addressing it, so I guess it's fine to go in.