Fix typo in postgres patch-drop-ar_text.sql

I18f1c7 was cherry-picked to REL1_31 but it was broken.
Before that got merged to REL1_31, this was already in master,
but apparently that was missed when cherry-picking.
This should have made 1.31-rc.2.

Bug: T205967
Change-Id: I6d479d
(cherry picked from commit 7e685a395d4a6e69d904c03f6e847b18795217a9)