pgsql: Revert commit a5b652f3a0.

Revert commit a5b652f3a0.

This commit reverts the fix "Make inherited TRUNCATE perform access
permission checks on parent table only" only in the back branches.

It's not hard to imagine that there are some applications expecting
the old behavior and the fix breaks their security. To avoid this
compatibility problem, we decided to apply the fix only in HEAD and
revert it in all supported back branches.

Discussion: https://postgr.es/m/21015.1580400165@sss.pgh.pa.us

Branch
------
REL_11_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/ea7857dddb54c371f70be7215ea3b72cb70265bf

Modified Files
--------------
src/backend/commands/tablecmds.c | 70 +++++++++-----------------------
src/test/regress/expected/privileges.out | 21 ----------
src/test/regress/sql/privileges.sql | 14 -------
3 files changed, 19 insertions(+), 86 deletions(-)