Remove radius from initdb authentication methods.

Remove radius from initdb authentication methods.

Commit a1643d40b removed RADIUS authentication, but apparently
overlooked initdb's list of accepted authentication methods.  As a
result, initdb still accepted radius for --auth, --auth-host, and
--auth-local, allowing it to create a pg_hba.conf that the server could
not load.

Remove radius from initdb's local and host authentication method lists.

Backpatch-through: 19
Author: Chao Li <lic@highgo.com>
Discussion: https://postgr.es/m/983F946B-A7CE-4C93-B5F0-665616F72254%40gmail.com