Remove some useless free calls.
These were introduced in recent commit
52e4f0cd47. We were trying to free
some transient space consumption and that too was not entirely correct and
complete. We don't need this partial freeing of memory as it will be
allocated just once for a query and will be freed at the end of the query.
Author: Zhihong Yu
Reviewed-by: Amit Kapila
Discussion: https://postgr.es/m/CALNJ-vQORfQ=vicbKA_RmeGZGzm1y3WsEcZqXWi7qjN43Cz_vg@mail.gmail.com