agent: Rename the delete menu item in the MCP section (#33265)

From "Delete" to "Uninstall" for clarity.

Release Notes:

- N/A

crates/agent/src/agent_configuration.rs

@@ -593,7 +593,7 @@ impl AgentConfiguration {
                             }
                         })
                         .separator()
-                        .entry("Delete", None, {
+                        .entry("Uninstall", None, {
                             let fs = fs.clone();
                             let context_server_id = context_server_id.clone();
                             let context_server_store = context_server_store.clone();