pgsql: doc: change pg_upgrade wal_level to be not minimal

doc: change pg_upgrade wal_level to be not minimal

Previously it was specified to be only replica.

Discussion: /messages/by-id/20200618180058.GK7349@momjian.us

Backpatch-through: 9.5

Branch
------
REL_11_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/457942e18853f168f03c4bae4b4c0dce494f68e2

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