Doc fix on information_schema.views

Hi,

Seems that per the documentation on information_schema.views [1] we do not support check_options ("Applies to a feature not available in PostgreSQL"). 

Attached is a patch that fix this description. As CHECK OPTION is supported since 9.4, the patch might be applied on all versions since 9.4.

[1] https://www.postgresql.org/docs/current/infoschema-views.html

-- 
Gilles Darold
http://www.darold.net/