collections.Counter: Formatted the code in the "See also" section.

collections.deque.remove: "Removed the first occurrence of value." -> "Remove ..."

collections.deque.index (a followup from issue23704):
    
Changed [, end] to [, stop] in the signature, because the implementation and the docstring of deque.index use 'stop'. Also, adapted the brief explanation from the Common Sequence Operations table.

https://docs.python.org/3/library/stdtypes.html#common-sequence-operations