pgsql: Fix BF failure introduced by commit b3f6b14cf4.

Fix BF failure introduced by commit b3f6b14cf4.

The test added by commit b3f6b14cf4 uses a non-superuser and forgot to set
up pg_hba.conf to allow connections from it. The special setup is only
needed on Windows machines that don't use UNIX sockets.

As per buildfarm

Discussion: https://postgr.es/m/CAJpy0uCfrSspV1x3VWkgamqyhYaUWQZpP0nqjJx4YPvKqN6P_A@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/def0ce3370689b939c6d7a3c3eb824d69989ef6e

Modified Files
--------------
src/test/recovery/t/040_standby_failover_slots_sync.pl | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)