Remove expected panic message from from_invalid_raw_fd_should_panic

It changed between 1.70 and current stable. Checking if the function
panics should be good enough.

Author: Thomasdezeeuw

tests/socket.rs

@@ -140,7 +140,6 @@ fn protocol_fmt_debug() {
 }
 
 #[test]
-#[should_panic = "fd != -1"]
 #[cfg(unix)]
 fn from_invalid_raw_fd_should_panic() {
     use std::os::unix::io::FromRawFd;