pgsql: Fix relation descriptor leak.

Fix relation descriptor leak.

We missed closing the relation descriptor while sending changes via the
root of partitioned relations during logical replication.

Author: Amit Langote and Mark Zhao
Reviewed-by: Amit Kapila and Ashutosh Bapat
Backpatch-through: 13, where it was introduced
Discussion: https://postgr.es/m/tencent_41FEA657C206F19AB4F406BE9252A0F69C06@qq.com
Discussion: https://postgr.es/m/tencent_6E296D2F7D70AFC90D83353B69187C3AA507@qq.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/044aa9e70e552d9adb4f6429a1b0e96dde946a92

Modified Files
--------------
src/backend/replication/pgoutput/pgoutput.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)