databases/postgresql*: update to latest versions

The PostgreSQL Global Development Group has released an update to all supported
versions of our database system, including 13.4, 12.8, 11.13, 10.18, and
9.6.23, as well as the third beta release of PostgreSQL 14. This release closes
one security vulnerability and fixes over 75 bugs reported over the last three
months.

Turn off parallel builds since we continue to struggle with build problems when
it is activated. [1]

Avoid chasing latest LLVM version. [2]

PR: 256466 [1], 256167 [2]
Release notes: https://www.postgresql.org/docs/release/
Security: b471130b-fb86-11eb-87db-6cc21735f730