input: Write a python function to find employees with salaries above a given threshold.
  assert find_high_earners(employee_data, 50000) == ["Andrew", "Mark"]
  assert find_high_earners(employee_data, 60000) == ["Mark"]
  assert find_high_earners(employee_data, 45000) == ["Andrew", "Mark"]
output: def find_high_earners(employee_data, threshold):
      return [name for name, salary in employee_data if salary > threshold]