input: Write a python function to find the most common word in a given text and its frequency after removing punctuation marks.
  assert most_common_word("This is a sentence. This is another sentence. Here is a long sentence. This sentence is the longest. Also, this sentence is the longest.") == ('sentence', 5)
  assert most_common_word("Hello world! Hello again. And hello once more.") == ('hello', 3)
  assert most_common_word("One fish, two fish, red fish, blue fish.") == ('fish', 4)
output: import re
  from collections import Counter
  
  def most_common_word(text):
      words = re.findall(r'\b\w+\b', text.lower())
      common_word, frequency = Counter(words).most_common(1)[0]
      return common_word, frequency