Fix sign in disclaimer to accurately show trial benefits (#55964)

Self-Review Checklist:

- [ x] I've reviewed my own diff for quality, security, and reliability
- [x ] Unsafe blocks (if any) have justifying comments
- [x ] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x ] Tests cover the new/changed behavior
- [x ] Performance impact has been considered and is acceptable

Release Notes:

- N/A

crates/ai_onboarding/src/ai_onboarding.rs

@@ -156,11 +156,11 @@ impl ZedAiOnboarding {
             .gap_1()
             .child(Headline::new("Welcome to Zed AI"))
             .child(
-                Label::new("Sign in to try Zed Pro for 14 days, no credit card required.")
+                Label::new("Sign in to try Zed Pro free for 14 days.")
                     .color(Color::Muted)
                     .mb_2(),
             )
-            .child(PlanDefinitions.pro_plan())
+            .child(PlanDefinitions.sign_in_upsell())
             .child(
                 Button::new("sign_in", "Try Zed Pro for Free")
                     .disabled(signing_in)

crates/ai_onboarding/src/plan_definitions.rs

@@ -14,6 +14,13 @@ impl PlanDefinitions {
             .child(ListBulletItem::new("Unlimited use of external agents"))
     }
 
+    pub fn sign_in_upsell(&self) -> impl IntoElement {
+        List::new()
+            .child(ListBulletItem::new("Unlimited edit predictions"))
+            .child(ListBulletItem::new("$20 of tokens in Zed agent"))
+            .child(ListBulletItem::new("No credit card required"))
+    }
+
     pub fn pro_trial(&self, period: bool) -> impl IntoElement {
         List::new()
             .child(ListBulletItem::new("$20 of tokens in Zed agent"))