Apply suggestions from code review

Co-authored-by: Robin Jadoul <robin.jadoul@gmail.com>

Author: erik-3milabs

spec/src/keccak_round.toml

@@ -34,7 +34,7 @@ desc = "the right-rotated component of `rotated_Cxz`"
 [[variables.auxiliary]]
 name = "Dxz"
 type = [["Byte", 8], 5]
-desc = "$#`Cxz[x,y,z]` xor #`rotated_Cxz[`\\(#`x` +1) mod 5#`,y,z]`$"
+desc = "$#`Cxz[`\\(#`x` - 1) mod 5#`,y,z]` xor #`rotated_Cxz[`\\(#`x` + 1) mod 5#`,y,z]`$"
 
 [[variables.auxiliary]]
 name = "theta"