UPDATING: Correct the dirname database/* to databases/*

In UPDATING, all sections which contain "database/..." instead of "databases/..." in the 'AFFECTS:' line, utilities like 'pkg updating' can't automatically display those sections.

The postgresql sections in particular have information that would be useful for casual use of "pkg updating". One work-around, of course, is to use "pkg updating database/postgresql"

While here, also correct some more occurrences.

PR: 249881
Submitted by: rhurlin
Reported by: Keith White <kwhite@site.uottawa.ca>
Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D26557