input: Write a python function to replace a given letter with a hyphen in a list of words.
  assert replaceLetter(["apple", "banana", "grape", "pear"], "a") == ['-pple', 'b-n-n-', 'gr-pe', 'pe-r']
  assert replaceLetter(["hello", "world"], "o") == ['hell-', 'w-rld']
  assert replaceLetter(["test", "replace", "letter"], "e") == ['t-st', 'r-plac-', 'l-tt-r']
output: def replaceLetter(words, letter):
      return [word.replace(letter, '-') for word in words]