Fix Incorrect Formula in CatalyticWall

This was a foolish mistake on my part. The reference I was reading had R/M, where R was the *universal* gas constant, not the species. However, I implemented the species. R/M is the species gas constant so we'll just use that. Updated unit and regression tests accordingly. Unit tests aren't much help when you make the same mistake twice…

This got picked out due to the unit change coming up in Antioch.