pgsql: Fix lock release for role membership grants in DROP OWNED BY.

Fix lock release for role membership grants in DROP OWNED BY.

Commit 6566133c5f5 added a case for AuthMemRelationId in
AcquireDeletionLock(), but not ReleaseDeletionLock(). The fall-through
case would go to UnlockDatabaseObject(), which would raise a WARNING;
and the lock would be retained until the end of the transaction.

Add the missing branch.

Discussion: https://postgr.es/m/2487ddcd737d4fc8e408e87aa9ad4365eed3bbb3.camel@j-davis.com
Backpatch-through: 16

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b48caa7dfde8991ee09226593c381bd3442297dc

Modified Files
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src/backend/catalog/dependency.c | 3 +++
src/test/isolation/expected/drop-owned-grant.out | 8 +++++++
src/test/isolation/isolation_schedule | 1 +
src/test/isolation/specs/drop-owned-grant.spec | 30 ++++++++++++++++++++++++
4 files changed, 42 insertions(+)