Missing default value of createrole_self_grant in document

[shiy.f...@fujitsu.com]

Hi hackers,

I noticed that the document of GUC createrole_self_grant doesn't mention its
default value. The attached patch adds that.

Regards,
Shi Yu

v1-0001-Add-default-value-of-createrole_self_grant-in-doc.patch
Description: v1-0001-Add-default-value-of-createrole_self_grant-in-doc.patch