(MAINT) Indicate supported PostgreSQL versions 
(MAINT) Indicate supported PostgreSQL versions 

Prior to this commit, there was an old limitation noted that we only support up to PostgreSQL 9.5.  

After this commit, we remove that limitation because we support whatever the default for each OS is.
puppetlabs/puppetlabs-postgresql,puppetlabs/puppetlabs-postgresql,buzzdeee/puppetlabs-postgresql,puppetlabs/puppetlabs-postgresql,buzzdeee/puppetlabs-postgresql,buzzdeee/puppetlabs-postgresql