fix(bigint): Remove unused check for BigInt lcm

The BigInt lcm defaults to the BigUInt::lcm() method which already includes the
check. There is no need to do it here as well.

src/bigint.rs

@@ -2188,11 +2188,7 @@ impl Integer for BigInt {
     /// Calculates the Lowest Common Multiple (LCM) of the number and `other`.
     #[inline]
     fn lcm(&self, other: &BigInt) -> BigInt {
-        if self.is_zero() && other.is_zero() {
-            Self::zero()
-        } else {
-            BigInt::from_biguint(Plus, self.data.lcm(&other.data))
-        }
+        BigInt::from_biguint(Plus, self.data.lcm(&other.data))
     }
 
     /// Deprecated, use `is_multiple_of` instead.