rotational-cipher: match test data to description (26 -> 0) (#660)
rotational-cipher: match test data to description (26 -> 0) (#660)

Test data (0) didn't match description (26).
Should effectively be the same test as the one above it due to modulus
math, but was literally the same test.
kgengler/x-common,exercism/x-common,exercism/x-common,ErikSchierboom/x-common,rpottsoh/x-common,petertseng/x-common,kgengler/x-common,jmluy/x-common,Vankog/problem-specifications,jmluy/x-common,jmluy/x-common,Vankog/problem-specifications,ErikSchierboom/x-common,rpottsoh/x-common,petertseng/x-common