[CHORE] Pin PyIceberg version to <0.8 (#3391)

Pinning because PyIceberg changes some internal APIs in v0.8 that we
currently use, which breaks our use case. Tracking progress on a fix in
#3394

pyproject.toml

@@ -28,7 +28,7 @@ azure = []
 deltalake = ["deltalake"]
 gcp = []
 hudi = ["pyarrow >= 8.0.0"]
-iceberg = ["pyiceberg >= 0.4.0", "packaging"]
+iceberg = ["pyiceberg >= 0.4.0, < 0.8", "packaging"]
 lance = ["lancedb"]
 numpy = ["numpy"]
 pandas = ["pandas"]