Protection of the protected sheet is removed after load_workbook and save it again

Issue #1261 new
saif almulazem created an issue

Hi, when I load an existing excel with protected sheets then 'openpyxl' removes all these protection (while workbook protection remains protected), this issues was not exists in V2.5 it appears after upgrading to V2.6 although V2.6 has a great improvements which I was looking for. Thanks in advance for your support