pgsql: Add note about unused arguments for pg_replication_origin_xact_r

Add note about unused arguments for pg_replication_origin_xact_reset() in docs.

In 9.5, two arguments were introduced into pg_replication_origin_xact_reset()
by mistake while they are actually not used at all. We cannot fix this issue
for 9.5 anymore because it needs a catalog version bump. Instead, we add
a note about those unused arguments into the document.

Reviewed-By: Andres Freund

Branch
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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/b07058c213725e9493052ffe0a219323f74e8ed3

Modified Files
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doc/src/sgml/func.sgml | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)