psql: Fix \df tab completion for procedures

psql: Fix \df tab completion for procedures

Commit fb421231daa extended \df to include procedures, but its tab
completion continued not to show procedures.

Update \df tab completion to include procedures as well.

Backpatch to all supported versions.

Author: Erik Wienhold <ewie@ewie.name>
Reviewed-by: Surya Poondla <suryapoondla4@gmail.com>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/10fbfdfe-80f6-4ef9-b8b3-f7be0eb53a50@ewie.name
Backpatch-through: 14