解决方法:
在迁移文件中up方法最上方加上下面这一行代码即可:
Schema::getConnection()->getDoctrineSchemaManager()->getDatabasePlatform()->registerDoctrineTypeMapping('enum', 'string');
例如:
public function up()
{
Schema::getConnection()->getDoctrineSchemaManager()->getDatabasePlatform()->registerDoctrineTypeMapping('enum', 'string');
Schema::table('medicines', function (Blueprint $table) { });
}