BUG #18816: pg16 requires perl 5.14+ but is not documented

The following bug has been logged on the website:

Bug reference:      18816
Logged by:          David Gilman
Email address:      davidgilman1@gmail.com
PostgreSQL version: 16.7
Operating system:   n/a
Description:

The PostgreSQL 16 branch's configure script checks to see if perl 5.14+ is
installed (see config/perl.m4) but there is no comment in the documentation
that perl 5.14+ is required in the postgresql16 docs like there is in the
postgresql17 docs. See doc pages:

https://www.postgresql.org/docs/16/install-requirements.html
https://www.postgresql.org/docs/17/install-requirements.html