Fixed 'news by mail' related message

Change-Id: I5f4943eeb6d5cd4aa9cf4e47265e9ed07d767a0e
Merge remote-tracking branch 'gerrit/5181_send_an_email_to_all_the_project_members' into stable

Change-Id: I16a34dcd8344ddbd6ad7ce96276c3dc504c0acf4
This is Tuleap 6.5.99.41

Change-Id: Ieb8bcf9aafb90ff357c55b32e97712090dc9b6da