Don't assume external ls (#4925)

crates/nu-command/tests/commands/which.rs

@@ -48,7 +48,7 @@ fn multiple_reports_for_alias_def_custom() {
     );
 
     let length: i32 = actual.out.parse().unwrap();
-    assert!(length >= 3);
+    assert!(length >= 2);
 }
 
 // `get_aliases_with_name` and `get_custom_commands_with_name` don't return the correct count of