fix of warning: the borrowed expression implements the required traits

```sh

warning: the borrowed expression implements the required traits
   --> src/lib.rs:151:23
    |
151 |         std::fs::copy(&src, &dest).with_context(|| {
    |                       ^^^^ help: change this to: `src`
    |
    = help: for further information visit
https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrows_for_generic_args
    = note: `#[warn(clippy::needless_borrows_for_generic_args)]` on by
default

warning: `cargo-ament-build` (lib) generated 1 warning (run `cargo
clippy --fix --lib -p cargo-ament-build` to apply 1 suggestion)
```

Author: Guelakais

src/lib.rs

@@ -148,7 +148,7 @@ fn copy(src: impl AsRef<Path>, dest_dir: impl AsRef<Path>) -> Result<()> {
             }
         }
     } else if src.is_file() {
-        std::fs::copy(&src, &dest).with_context(|| {
+        std::fs::copy(src, &dest).with_context(|| {
             format!(
                 "Failed to copy '{}' to '{}'.",
                 src.display(),