cloud_llm_client: Add another Plan variant (#37852)

This PR adds a corresponding `FreeV2` variant to the `Plan`.

Release Notes:

- N/A

crates/language_model/src/model/cloud_model.rs

@@ -36,7 +36,9 @@ impl fmt::Display for ModelRequestLimitReachedError {
             Plan::ZedProTrial => {
                 "Model request limit reached. Upgrade to Zed Pro for more requests."
             }
-            Plan::ZedProV2 | Plan::ZedProTrialV2 => "Model request limit reached.",
+            Plan::ZedFreeV2 | Plan::ZedProV2 | Plan::ZedProTrialV2 => {
+                "Model request limit reached."
+            }
         };
 
         write!(f, "{message}")