Why this fontconfig warning?

[Joe Lowder]

Can someone please explain to me why I am seeing the
fontconfig warning quoted below every time I run this:

/usr/lib/libreoffice/program/swriter

(And what change do I need to make
to stop this from appearing?)

Fontconfig warning: "/etc/fonts/conf.d/50-user.conf", line 14: reading
configurations from ~/.fonts.conf is deprecated. please move it to
/home/joe/.config/fontconfig/fonts.conf manually

Here is the content of 50-user.conf:
lrwxrwxrwx 1 26 Aug 16  2016 50-user.conf -> ../conf.avail/50-user.conf
t420: cat 50-user.conf
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
        <!--
            Load per-user customization files where stored on XDG Base
Directory
            specification compliant places. it should be usually:
              $HOME/.config/fontconfig/conf.d
              $HOME/.config/fontconfig/fonts.conf
        -->
        <include ignore_missing="yes"
prefix="xdg">fontconfig/conf.d</include>
        <include ignore_missing="yes"
prefix="xdg">fontconfig/fonts.conf</include>
        <!-- the following elements will be removed in the future -->
        <include ignore_missing="yes"
deprecated="yes">~/.fonts.conf.d</include>
        <include ignore_missing="yes"
deprecated="yes">~/.fonts.conf</include>
</fontconfig>

Here are the entries at the two referenced locations:
(1) /home/joe
-rw-r--r-- 1  761 Dec 30  2016 .fonts.conf

(2) /home/joe/.config/fontconfig
-rw-r--r-- 1 509 Oct 17  2015 fonts.conf.old
-rw-r--r-- 1 761 Dec 30  2016 fonts.conf