Silence warning in miri tests.

Author: cjgillot

src/tools/miri/tests/fail/function_calls/arg_inplace_observe_after.rs

@@ -22,6 +22,7 @@ fn main() {
     }
 }
 
+#[expect(unused_variables, unused_assignments)]
 pub fn change_arg(mut x: S) {
     x.0 = 0;
 }

src/tools/miri/tests/fail/function_calls/arg_inplace_observe_during.rs

@@ -23,6 +23,7 @@ fn main() {
     }
 }
 
+#[expect(unused_variables, unused_assignments)]
 pub fn change_arg(mut x: S, ptr: *mut S) {
     x.0 = 0;
     // If `x` got passed in-place, we'd see the write through `ptr`!

src/tools/miri/tests/pass/align_repeat_into_well_aligned_array.rs

@@ -2,6 +2,7 @@
 
 use std::mem::size_of;
 
+#[expect(unused_variables, unused_assignments)]
 fn main() {
     let mut a = Params::new();
     // The array itself here happens to be quite well-aligned, but not all its elements have that