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.
11 jobs for native-emoji-picker in 16 minutes and 57 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #9160
clazy

00:01:06

passed #9161
qmllint

00:01:01

 
  Build
passed #9165
archlinux

00:00:56

passed #9164
debian-sid

00:00:52

passed #9163
neon-bionic

00:01:02

passed #9162
ubuntu-trusty

00:00:54

 
  Deploy
passed #9169
allowed to fail
android

00:04:41

passed #9167
allowed to fail
click-xenial

00:06:46

passed #9166
allowed to fail
linux-appimage

00:05:13

passed #9170
allowed to fail
mac-osxcross

00:03:47

passed #9168
allowed to fail
windows-mxe

00:04:44