pgsql: Suppress DETAIL output from an event_trigger test.

Suppress DETAIL output from an event_trigger test.

Suppress 3 lines of unstable DETAIL output from a DROP ROLE statement in
event_trigger.sql. This is further cleanup for commit dd299df8.

Note that the event_trigger test instability issue is very similar to
the recently suppressed foreign_data test instability issue. Both
issues involve DETAIL output for a DROP ROLE statement that needed to be
changed as part of dd299df8.

Per buildfarm member macaque.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/05f110cc0b83d9dc174f72cf96798299eb3e7f67

Modified Files
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src/test/regress/expected/event_trigger.out | 6 +++---
src/test/regress/sql/event_trigger.sql | 3 +++
2 files changed, 6 insertions(+), 3 deletions(-)