pgsql: doc: Fix data_checksums data type

doc: Fix data_checksums data type

Commit f19c0eccae96 changed the data_checksums GUC datatype from a
boolean to an enum. This updates the documentation to accurately
reflect its new type and document the new possible states: 'on',
'off', 'inprogress-on', and 'inprogress-off'.

Also update the xref for more information to point to the section
on data checksums rather than the initdb checksum option.

Author: Lakshmi N <lakshmin(dot)jhs(at)gmail(dot)com>
Reviewed-by: Daniel Gustafsson <daniel(at)yesql(dot)se>
Discussion: https://postgr.es/m/CA+3i_M-AtTnqTB2KLBTpu-c-jvnTuy7bGxyxs80rgiQLxWrRUQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b364828f825a5914a21140145186365021ac0bc4

Modified Files
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doc/src/sgml/config.sgml | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)