I'd stick with it, it's only two days and you might be surprised that it's more difficult than you expect. When I was doing C25k, the 20 min run wasn't too bad, but I did have a harder time with week 6. I think part of the purpose of week 6 is also to give your body a bit of a break. W5D3 is the first big run in the program, and it's good to back off for a couple days before starting week 7. Or at least that's my take on it!

I did end up skipping week 8 though. Week 7 went well for me so I just went right to week 9.