pgsql: Revert commit 4b96c03a0a.

Revert commit 4b96c03a0a.

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_10_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/8b1a6499d055f6f222e200fd6410073537d11f31

Modified Files
--------------
src/backend/commands/tablecmds.c | 69 +++++++++-----------------------
src/test/regress/expected/privileges.out | 21 ----------
src/test/regress/sql/privileges.sql | 14 -------
3 files changed, 19 insertions(+), 85 deletions(-)