[oss] Update deadline for 2nd assignment

[Razvan Deaconescu]

Hi, everyone!

As discussed during the lecture this Monday, the deadline for the 2nd
assignment is extended to Sunday, April 28, 11PM. See the wiki[1].

Don't forget to add Vlad Dumitrescu, Lucian Cojocar and Răzvan
Deaconescu to your GitLab projects and don't hesitate to contact us and
ask for hints.

[1] http://elf.cs.pub.ro/oss/wiki/assignments/assignment-2

Razvan