chore: update stderr for new msrv

Author: mriise

derive/tests/fail/no_allow_same_code_twice.stderr

@@ -10,4 +10,4 @@ warning: unused variable: `input`
 7 |     fn update(&mut self, input: &[u8]) { }
   |                          ^^^^^ help: if this is intentional, prefix it with an underscore: `_input`
   |
-  = note: `#[warn(unused_variables)]` on by default
+  = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default

derive/tests/fail/no_allow_same_name_twice.stderr

@@ -15,7 +15,7 @@ warning: unused variable: `input`
 7 |     fn update(&mut self, input: &[u8]) { }
   |                          ^^^^^ help: if this is intentional, prefix it with an underscore: `_input`
   |
-  = note: `#[warn(unused_variables)]` on by default
+  = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default
 
 error[E0004]: non-exhaustive patterns: `&Code::Foo` not covered
   --> tests/fail/no_allow_same_name_twice.rs:16:17
@@ -46,4 +46,4 @@ warning: unreachable pattern
 22 | |      Foo,
    | |________^ no value can reach this
    |
-   = note: `#[warn(unreachable_patterns)]` on by default
+   = note: `#[warn(unreachable_patterns)]` (part of `#[warn(unused)]`) on by default