[docs] tuple or struct_time

Functions in the time module that expect broken down time are currently documented as accepting "tuple or struct_time". For example,

http://docs.python.org/py3k/library/time.html#time.strftime

However, in recent versions, ".. or struct_time" is redundant because

...

...

issubclass(time.struct_time, tuple)

True

I think it would be more informative for a reader to change "tuple or struct_time" to "9-tuple".