update docs

Author: kevinjqliu

mkdocs/docs/api.md

@@ -1941,7 +1941,7 @@ PyIceberg integrates with [Apache DataFusion](https://datafusion.apache.org/) th
 
     The integration has a few caveats:
 
-    - Only works with `datafusion >= 45, < 49`
+    - Only works with `datafusion == 51`, aligns with the version used in `pyiceberg-core`
     - Depends directly on `iceberg-rust` instead of PyIceberg's implementation
     - Has limited features compared to the full PyIceberg API