pgsql: Fix documentation for the privileges required for replication fu

Fix documentation for the privileges required for replication functions.

Previously it's documented that use of replication functions is
restricted to superusers. This is true for the functions which
use replication origin, but not for pg_logicl_emit_message() and
functions which use replication slot. For example, not only
superusers but also users with REPLICATION privilege is allowed
to use the functions for replication slot. This commit fixes
the documentation for the privileges required for those replication
functions.

Back-patch to 9.4 (all supported versions).

Author: Matsumura Ryo
Discussion: https://postgr.es/m/03040DFF97E6E54E88D3BFEE5F5480F74ABA6E16@G01JPEXMBYT04

Branch
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REL_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/704637d8d935bee52f748641a0620e2e83de07d2

Modified Files
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doc/src/sgml/func.sgml | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)