[docs] document bug

[Dwight Livingston]

https://docs.python.org/3/glossary.html#glossary

[Delete first "either" in following paragraph]

struct sequence
    A tuple with named elements. Struct sequences expose an interface
    similar to named tuple
    <https://docs.python.org/3/glossary.html#term-named-tuple> in that
    elements can _*either*_ be accessed either by index or as an
    attribute. However, they do not have any of the named tuple methods
    like |_make()|
    <https://docs.python.org/3/library/collections.html#collections.somenamedtuple._make>
    or |_asdict()|
    <https://docs.python.org/3/library/collections.html#collections.somenamedtuple._asdict>.
    Examples of struct sequences include |sys.float_info|
    <https://docs.python.org/3/library/sys.html#sys.float_info> and the
    return value of |os.stat()|
    <https://docs.python.org/3/library/os.html#os.stat>.