docs: Note pyiceberg only works with datafusion < 49

[Datafusion >= 49 is not backward compatible](apache/iceberg-rust#1647 (comment))

Author: manuzhang

mkdocs/docs/api.md

@@ -1939,7 +1939,7 @@ PyIceberg integrates with [Apache DataFusion](https://datafusion.apache.org/) th
 
     The integration has a few caveats:
 
-    - Only works with `datafusion >= 45`
+    - Only works with `datafusion >= 45, < 49`
     - Depends directly on `iceberg-rust` instead of PyIceberg's implementation
     - Has limited features compared to the full PyIceberg API