pidof: don't require program name as arg

src/uu/pidof/src/pidof.rs

@@ -117,7 +117,6 @@ pub fn uu_app() -> Command {
         .arg(
             Arg::new("program-name")
                 .help("Program name.")
-                .required(true)
                 .index(1)
                 .action(ArgAction::Append),
         )

tests/by-util/test_pidof.rs

@@ -26,7 +26,7 @@ fn test_find_kthreadd() {
 #[test]
 #[cfg(target_os = "linux")]
 fn test_no_program() {
-    new_ucmd!().fails().code_is(1);
+    new_ucmd!().fails().code_is(1).no_output();
 }
 
 #[test]