[Bugfix:CourseMaterials] Backwards compatible URLs (#6973)
[Bugfix:CourseMaterials] Backwards compatible URLs (#6973)

* Fix URL error

* Fix download link

Co-authored-by: Chris Reed <aab780deaa45ed0af851c804a13faef6b70737e7@users.noreply.github.com>
RCOS-Grading-Server/HWserver,Submitty/Submitty,RCOS-Grading-Server/HWserver,RCOS-Grading-Server/HWserver,Submitty/Submitty,Submitty/Submitty,Submitty/Submitty,Submitty/Submitty,RCOS-Grading-Server/HWserver,RCOS-Grading-Server/HWserver,RCOS-Grading-Server/HWserver,RCOS-Grading-Server/HWserver,Submitty/Submitty,Submitty/Submitty,RCOS-Grading-Server/HWserver,Submitty/Submitty,Submitty/Submitty,RCOS-Grading-Server/HWserver