core: Minor cleanup

Author: Daiki Mizukami

src/libcore/num/mod.rs

@@ -1765,7 +1765,7 @@ assert_eq!((-a).mod_euc(-b), 1);
             pub fn mod_euc(self, rhs: Self) -> Self {
                 let r = self % rhs;
                 if r < 0 {
-                    if rhs.is_negative() {
+                    if rhs < 0 {
                         r - rhs
                     } else {
                         r + rhs