pgsql: Fix some shadow variables in src/backend/replication/

Fix some shadow variables in src/backend/replication/

The code is able to compile already without warnings under
-Wshadow=compatible-local, which is itself already enabled in the tree,
and the ones fixed here showed up with the more restrictive -Wshadow.

There are more of these that we may want to look at, and the ones fixed
here made the code confusing.

Author: Peter Smith
Discussion: https://postgr.es/m/CAHut+PuR0y4ofNOxi691VTVWmBfScHV9AaBMGSpeh8+DKp81Nw@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b5934bfd6071fed3a38cea0cfaa93afda63d9c0c

Modified Files
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src/backend/replication/logical/logicalfuncs.c  | 4 ++--
src/backend/replication/logical/reorderbuffer.c | 6 +++---
src/backend/replication/walsender.c             | 8 ++++----
3 files changed, 9 insertions(+), 9 deletions(-)