Ignore trivially_copy_pass_by_ref pedantic clippy lint in test

    warning: this argument (4 byte) is passed by reference, but would be more efficient if passed by value (limit: 8 byte)
      --> test_suite/tests/regression/issue2844.rs:18:28
       |
    18 |     pub fn serialize<S>(_: &i32, _: S) -> Result<S::Ok, S::Error>
       |                            ^^^^ help: consider passing by value instead: `i32`
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#trivially_copy_pass_by_ref
       = note: `-W clippy::trivially-copy-pass-by-ref` implied by `-W clippy::pedantic`
       = help: to override `-W clippy::pedantic` add `#[allow(clippy::trivially_copy_pass_by_ref)]`

test_suite/tests/regression/issue2844.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::trivially_copy_pass_by_ref)]
+
 use serde_derive::{Deserialize, Serialize};
 
 macro_rules! declare_in_macro {