MOSCOW — North Korea sealed its borders more than a year ago because of the pandemic, grounding flights and shutting its frontier with neighboring China and Russia. This week, a few Russian diplomats found a way out. Russia’s Foreign Ministry said on Friday that eight employees and family members at its embassy in North Korea had taken an unusual route — one that included a bus ride and a trip on a hand-pushed railcar — to reach and cross the country’s border with Russia. The group included the