31 FEB executes immediately

[snus8bit]

Describe the bug

Minor bug. Schedule with non-existent day like "* * * 31 FEB *" executes immediately.

To Reproduce

package main

import (
	"fmt"
	"log"

	"github.com/go-co-op/gocron/v2"
)

func main() {
	c := make(chan struct{})
	s, err := gocron.NewScheduler()
	if err != nil {
		log.Fatal(err)
	}
	if _, err := s.NewJob(gocron.CronJob("* * * 31 FEB *", true), gocron.NewTask(func() {
		fmt.Println("started")
		c <- struct{}{}
	})); err != nil {
		log.Fatal(err)
	}
	s.Start()
	<-c
}

Expected behavior

Never to execute.