pgsql: Fix memory leak due to LogicalRepRelMapEntry.attrmap.

Fix memory leak due to LogicalRepRelMapEntry.attrmap.

When rebuilding the relation mapping on subscribers, we were not releasing
the attribute mapping's memory which was no longer required.

The attribute mapping used in logical tuple conversion was refactored in
PG13 (by commit e1551f96e6) but we forgot to update the related code that
frees the attribute map.

Author: Hou Zhijie
Reviewed-by: Amit Langote, Amit Kapila, Shi yu
Backpatch-through: 10, where it was introduced
Discussion: https://postgr.es/m/OSZPR01MB6310F46CD425A967E4AEF736FDA49@OSZPR01MB6310.jpnprd01.prod.outlook.com

Branch
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REL_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/d873b5a5a34069a316df77285b231b792aee1349

Modified Files
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src/backend/replication/logical/relation.c | 7 +++++++
1 file changed, 7 insertions(+)