pgsql: Adjust documentation for syncfs().

Adjust documentation for syncfs().

Commit 8c16ad3b43 created a new appendix for syncfs(), which is
excessive for such a small amount of content. This commit moves
the description of the caveats to be aware of when using syncfs()
back to the documentation for recovery_init_sync_method. The
documentation for the other utilities with syncfs() support now
directs readers to recovery_init_sync_method for information about
these caveats.

Reported-by: Peter Eisentraut, Robert Haas
Suggested-by: Robert Haas
Reviewed-by: Robert Haas
Discussion: https://postgr.es/m/42804669-7063-1320-ed37-3226d5f1067d%40eisentraut.org
Discussion: https://postgr.es/m/CA%2BTgmobUiqKr%2BZMCLc5Qap-sXBnjfGUU%2BZBmzYEjUuWyjsGr1g%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/44a4cca9913bae8557c31207adb97b94e6e60603

Modified Files
--------------
doc/src/sgml/config.sgml | 12 +++++++++---
doc/src/sgml/filelist.sgml | 1 -
doc/src/sgml/postgres.sgml | 1 -
doc/src/sgml/ref/initdb.sgml | 4 ++--
doc/src/sgml/ref/pg_basebackup.sgml | 4 ++--
doc/src/sgml/ref/pg_checksums.sgml | 4 ++--
doc/src/sgml/ref/pg_combinebackup.sgml | 4 ++--
doc/src/sgml/ref/pg_dump.sgml | 5 +++--
doc/src/sgml/ref/pg_rewind.sgml | 4 ++--
doc/src/sgml/ref/pgupgrade.sgml | 4 ++--
doc/src/sgml/syncfs.sgml | 36 ----------------------------------
11 files changed, 24 insertions(+), 55 deletions(-)