algo(math): fix for loop break statement with <=

algorithms/math/is-prime.cpp

@@ -2,7 +2,7 @@ bool isprime(ll n) {
   if (n < 2) return false;
   if (n == 2) return true;
   if (n % 2 == 0) return false;
-  for (ll i = 3; i * i < n; i += 2)
+  for (ll i = 3; i * i <= n; i += 2)
     if (n % i == 0) return false;
   return true;
 }