pgsql: Revert commit 56bc82a511.

Revert commit 56bc82a511.

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
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REL9_4_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/d034ab0bb2ae9300e91f9272abd4872bf53ce8d7

Modified Files
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src/backend/commands/tablecmds.c         | 67 +++++++++-----------------------
src/test/regress/expected/privileges.out | 21 ----------
src/test/regress/sql/privileges.sql      | 14 -------
3 files changed, 18 insertions(+), 84 deletions(-)