[Fix](parquet-reader) Fix dict cols not be converted back to string t…

…ype in some cases. (apache#19348)

Fix dict cols not be converted back to string type in some cases, which includes introduced by apache#19039.
For dict cols, we will convert dict cols to int32 type firstly, then convert back to string type after read block. 
The block will be reuse it, so it is necessary to convert it back.

be/src/vec/exec/format/parquet/vparquet_group_reader.cpp

@@ -301,6 +301,7 @@ Status RowGroupReader::next_batch(Block* block, size_t batch_size, size_t* read_
         RETURN_IF_ERROR(_fill_missing_columns(block, *read_rows, _lazy_read_ctx.missing_columns));
 
         if (block->rows() == 0) {
+            _convert_dict_cols_to_string_cols(block);
             *read_rows = block->rows();
             return Status::OK();
         }
@@ -457,6 +458,7 @@ Status RowGroupReader::_do_lazy_read(Block* block, size_t batch_size, size_t* re
                 *read_rows = 0;
                 *batch_eof = true;
                 _lazy_read_filtered_rows += pre_read_rows;
+                _convert_dict_cols_to_string_cols(block);
                 return Status::OK();
             }
         } else {