Updated prelab link
Updated prelab link

Prelab 3 was changed to prelab 2 and pointed at the current github classroom.  We might want to consider not hard-coding it to the github classroom (since that would have to be updated every year) and instead refer to the canvas assignment... something to consider anway.
UMM-CSci-Systems/C-Lab-Starter,UMM-CSci-Systems/C-Lab-Starter