pgsql: Remove the flaky check in event_trigger_login regression test

Remove the flaky check in event_trigger_login regression test

The query checks that pg_database.dathasloginevt is unset on connect when
there are no event triggers. However, unsetting this flag is implemented in
a non-blocking way, so a concurrent autovacuum connection breaks this check.
It doesn't seem we can do much with this, at least within a regression test.
So, remove it.

Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/44807d19-81a6-3884-3e0f-22dd99aac3ed%40gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/4b885d01f9676f62d8b8156e45282c631181369f

Modified Files
--------------
src/test/regress/expected/event_trigger_login.out | 6 ------
src/test/regress/sql/event_trigger_login.sql | 1 -
2 files changed, 7 deletions(-)