pgsql: Default monitoring roles - errata

Default monitoring roles - errata

25fff40798fc4ac11a241bfd9ab0c45c085e2212 introduced
default monitoring roles. Apply these corrections:

* Allow access to pg_stat_get_wal_senders()
  by role pg_read_all_stats

* Correct comment in pg_stat_get_wal_receiver()
  to show it is no longer superuser-only.

Author: Feike Steenbergen
Reviewed-by: Michael Paquier

Apply to HEAD, then later backpatch to 10

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/6668a54eb8ef639a3182ae9e37e4e67982c44292

Modified Files
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src/backend/replication/walreceiver.c | 3 ++-
src/backend/replication/walsender.c   | 8 +++++---
2 files changed, 7 insertions(+), 4 deletions(-)