Update generate.rs

Co-authored-by: Stefan Holderbach <sholderbach@users.noreply.github.com>

crates/nu-command/src/generators/generate.rs

@@ -199,7 +199,7 @@ fn get_initial_state(
                     msg: "Missing initial value".to_string(),
                     span: Some(span),
                     help: Some(
-                        "Providing <initial> value to generate, or assigning default value to closure parameter"
+                        "Provide an <initial> value as an argument to generate, or assign a default value to the closure parameter"
                             .to_string(),
                     ),
                     inner: vec![],