Fix outdated comments regarding TupleTableSlots
The tts_flag is named TTS_FLAG_SHOULDFREE, so use that instead of
TTS_SHOULDFREE, which is the name of the macro that checks for that flag.
Additionally,
4da597edf got rid of the TupleTableSlot.tts_tuple field but
forgot to update a comment which referenced that field. Fix that.
Reported-by: Zhen Mingyang <zhenmingyang@yeah.net>
Reported-by: Richard Guo <guofenglinux@gmail.com>
Discussion: https://postgr.es/m/
1a96696c.9d3.
187193989c3.Coremail.zhenmingyang@yeah.net