agent: Update pieces of copy in the settings view (#35621)

Some tiny updates to make the agent panel's copywriting sharper.

Release Notes:

- N/A

crates/language_models/src/provider/open_ai.rs

@@ -780,7 +780,7 @@ impl Render for ConfigurationView {
         let api_key_section = if self.should_render_editor(cx) {
             v_flex()
                 .on_action(cx.listener(Self::save_api_key))
-                .child(Label::new("To use Zed's assistant with OpenAI, you need to add an API key. Follow these steps:"))
+                .child(Label::new("To use Zed's agent with OpenAI, you need to add an API key. Follow these steps:"))
                 .child(
                     List::new()
                         .child(InstructionListItem::new(