input: Write a python function to normalize annotations in a given sentence by removing the references in square brackets.
  assert normalizeAnnotations("This is a test sentence [1] with some references [2].") == "This is a test sentence  with some references ."
  assert normalizeAnnotations("Another sentence [3][4] with multiple references.") == "Another sentence   with multiple references."
  assert normalizeAnnotations("No references here.") == "No references here."
output: def normalizeAnnotations(sentence):
      import re
      return re.sub(r'\[\d+\]', '', sentence)