Update limits.mdx (#21904)

update max gateways for paid plan

Author: kathayl

src/content/docs/ai-gateway/reference/limits.mdx

@@ -15,7 +15,8 @@ The following limits apply to gateway configurations, logs, and related features
 | [Cache TTL](/ai-gateway/configuration/caching/#cache-ttl-cf-aig-cache-ttl)     | 1 month               |
 | [Custom metadata](/ai-gateway/configuration/custom-metadata/)    | 5 entries per request               |
 | [Datasets](/ai-gateway/evaluations/set-up-evaluations/)          | 10 per gateway                      |
-| Gateways                                                         | 10 per account                      |
+| Gateways free plan                                               | 10 per account                      |
+| Gateways paid plan                                               | 20 per account                      |
 | Gateway name length                                              | 64 characters                       |
 | Log storage rate limit                                           | 500 logs per second per gateway     |
 | Logs stored [paid plan](/ai-gateway/reference/pricing/)          | 10 million per gateway <sup>1</sup> |