tests/cp: remove FreeBSD guard in FIFO copy test

Copying FIFOs now work under FreeBSD and other UNIX platforms.

tests/by-util/test_cp.rs

@@ -3437,15 +3437,9 @@ fn test_same_file_force_backup() {
 }
 
 /// Test for copying the contents of a FIFO as opposed to the FIFO object itself.
-#[cfg(all(unix, not(target_os = "freebsd"), not(target_os = "openbsd")))]
+#[cfg(unix)]
 #[test]
 fn test_copy_contents_fifo() {
-    // TODO this test should work on FreeBSD, but the command was
-    // causing an error:
-    //
-    // cp: 'fifo' -> 'outfile': the source path is neither a regular file nor a symlink to a regular file
-    //
-    // the underlying `std::fs:copy` doesn't support copying fifo on freeBSD
     let scenario = TestScenario::new(util_name!());
     let at = &scenario.fixtures;