Update limits.mdx (#17741)

Author: kathayl

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

@@ -11,6 +11,7 @@ The following limits apply to gateway configurations, logs, and related features
 
 | Feature                                                         | Limit                               |
 | --------------------------------------------------------------- | ----------------------------------- |
+| Maximum datasets                                                | 10 per gateway                      |
 | Maximum gateways                                                | 10 per account                      |
 | Maximum logs stored [paid plan](/ai-gateway/reference/pricing/) | 10 million per gateway <sup>1</sup> |
 | Maximum logs stored [free plan](/ai-gateway/reference/pricing/) | 100,000 per account <sup>2</sup>    |