update of the file listing known contributors to the OTB project

Updated the file used by the OTB project's CI/contributors_check.sh script to detect new contributors, taking into account changes made to the .mailmap file in the same project.

To avoid any failures or alerts in the OTB project's CI/CD pipeline, this MR must be validated just before the other MR performed on the OTB project, relating to the update of the .mailmap file (otb!1072 (merged)).