Fix example in docs on documentation

src/doc/rustdoc.md

@@ -51,7 +51,7 @@ Calculates the factorial of a number.
 
 Given the input integer `n`, this function will calculate `n!` and return it.
 "]
-pub fn factorial(n: int) -> int { if n < 2 {1} else {n * factorial(n)} }
+pub fn factorial(n: int) -> int { if n < 2 {1} else {n * factorial(n - 1)} }
 # fn main() {}
 ~~~