fix target has dup

Author: kevinjqliu

pyiceberg/table/upsert_util.py

@@ -62,9 +62,11 @@ def get_rows_to_update(source_table: pa.Table, target_table: pa.Table, join_cols
     """
     all_columns = set(source_table.column_names)
     join_cols_set = set(join_cols)
-
     non_key_cols = list(all_columns - join_cols_set)
 
+    if has_duplicate_rows(target_table, join_cols):
+        raise ValueError("Target table has duplicate rows, aborting upsert")
+
     if len(target_table) == 0:
         # When the target table is empty, there is nothing to update :)
         return source_table.schema.empty_table()