pgsql: doc: Add default value of createrole_self_grant

doc: Add default value of createrole_self_grant

Document that the default value for createrole_self_grant is an empty
string which in turn disable the feature.

Author: Shi Yu <shiy.fnst@fujitsu.com>
Discussion: https://postgr.es/m/OSZPR01MB63105D0D96A9A72A7FCD4FFEFDA09@OSZPR01MB6310.jpnprd01.prod.outlook.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/e00bc6c92277bdfb9dc6b56df067b22f549e43b8

Modified Files
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doc/src/sgml/config.sgml | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)