merge-ort: drop unnecessary show_all_errors from collect_merge_info()

collect_merge_info() has set info.show_all_errors = 1 since d2bc1994f363 (merge-ort: implement a very basic collect_merge_info(), 2020-12-13). This setting was copied from unpack-trees.c where it controls batching of error messages for porcelain display, but merge-ort has no such error-batching logic and never needed it. With show_all_errors set, traverse_trees() captures a negative callback return but continues processing remaining entries rather than stopping immediately. Removing the setting restores the default behavior where a negative return from collect_merge_info_callback() breaks out of the traversal loop right away, allowing a future commit to exit early when a corrupt tree is detected. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>