Shell has agreed to sell its onshore business in Nigeria’s Niger Delta to a consortium of companies in a deal worth $2.4 billion (€2.2 billion), the latest move by the energy company to limit its exposure in the West African nation amid long-running complaints of environmental pollution caused by the oil industry. Shell called it a way to streamline its business in a country it has operated in for decades, facing pushback about oil spills that have fouled rivers and farms and exacerbated tensions in a region that has faced years of militant violence. “This agreement marks an important mileston…