docs: streamline features legend for better readability (#22577)

Author: yahonda

tidb-cloud/features.md

@@ -11,10 +11,10 @@ This document lists the feature support status for different TiDB Cloud plans, i
 >
 > [TiDB Cloud Starter](/tidb-cloud/select-cluster-tier.md#starter) is the best way to get started with TiDB Cloud. Additionally, you can try out TiDB Cloud features on [TiDB Playground](https://play.tidbcloud.com/?utm_source=docs&utm_medium=tidb_cloud_quick_start).
 
-- ✅: The feature is **generally available** or in **public preview**.
-- 🔒: The feature is in **private preview**.
-- 🚧: The feature is **under development**.
-- ❌: The feature is **currently not available**.
+- ✅: **Generally available** or **in public preview**.
+- 🔒: **In private preview**.
+- 🚧: **Under development**.
+- ❌: **Currently not available**.
 
 <table><thead>
   <tr>