Update variables.json (#21547)

Author: qiancai

variables.json

@@ -2,7 +2,7 @@
   "tidb": "TiDB",
   "tidb-version": "v8.5.0",
   "self-managed": "TiDB Self-Managed",
-  "starter": "TiDB Cloud Serverless",
+  "starter": "TiDB Cloud Starter",
   "essential": "TiDB Cloud Essential",
   "dedicated": "TiDB Cloud Dedicated",
   "console-url": "tidbcloud.com"