Use default font in emoji picker

This fix the emoji picker to present the real system emoji that would
 appear in the message view.
There is no reason to present emojis for a font the message view will
 not render identically.
12 jobs for native-emoji-picker in 18 minutes and 40 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #8553
clazy

00:00:47

passed #8554
qmllint

00:00:19

 
  Build
passed #8558
archlinux

00:00:54

passed #8557
debian-sid

00:00:49

passed #8556
neon-bionic

00:01:02

passed #8555
ubuntu-trusty

00:00:53

 
  Deploy
passed #8562
android

00:04:45

passed #8560
click-xenial

00:06:29

passed #8559
allowed to fail
linux-appimage

00:05:05

passed #8563
mac-osxcross

00:04:15

passed #9006
windows-mxe

00:05:06

failed #8561
windows-mxe

00:00:28