Add #[allow(dead_code)] in some tests

rust-version

@@ -1 +1 @@
-c5cbf7852a7692c7c51df64c09a59e7838b55202
+4e880f8cbc191374ce7db335962489f41d6d4e3e

tests/compile-fail/validity/invalid_wide_raw.rs

@@ -4,6 +4,7 @@ fn main() {
     trait T { }
     #[derive(Debug)]
     struct S {
+        #[allow(dead_code)]
         x: * mut dyn T
     }
     dbg!(S { x: unsafe { std::mem::transmute((0usize, 0usize)) } }); //~ ERROR: encountered dangling vtable pointer in wide pointer

tests/run-pass/issue-3794.rs

@@ -6,6 +6,7 @@ trait T {
 
 #[derive(Debug)]
 struct S {
+    #[allow(dead_code)]
     s: isize,
 }