input: Write a python function to generate a frequency table from a 2D list of integers and print it.
  assert print_freq_table([[1, 2], [3, 4]]) == None
  assert print_freq_table([[5, 10, 15], [20, 25, 30], [35, 40, 45]]) == None
  assert print_freq_table([[2, 4], [6, 8], [10, 12]]) == None
output: def print_freq_table(matrix):
      from collections import Counter
      
      # Flatten the 2D list into a 1D list
      flattened_list = [item for sublist in matrix for item in sublist]
      
      # Create a frequency table using Counter
      frequency_table = Counter(flattened_list)
      
      # Print the frequency table
      for key, value in sorted(frequency_table.items()):
          print(f"{key}: {value}")