tee: fix warning from ref_as_ptr lint in test

Author: cakebaker

tests/by-util/test_tee.rs

@@ -172,7 +172,7 @@ mod linux_only {
 
         let mut fds: [c_int; 2] = [0, 0];
         assert!(
-            (unsafe { libc::pipe(&mut fds as *mut c_int) } == 0),
+            (unsafe { libc::pipe(std::ptr::from_mut::<c_int>(&mut fds[0])) } == 0),
             "Failed to create pipe"
         );