background: Render thumbnails at 16:9

It's a much more common aspect ration nowadays, and makes
the whole panel look much nicer.
11 jobs for <span class="ref-name">gbsneto/background</span> in 118 minutes and 43 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #306340
build

00:01:22

 
  Test
passed #306342
asan

00:01:25

passed #306341
test

00:01:14

 
  Manual
manual #306347
allowed to fail manual
armv8
passed #306343
allowed to fail manual
flatpak

01:55:55

manual #306346
allowed to fail manual
msan
manual #306348
allowed to fail manual
ppc64le
manual #306344
allowed to fail manual
tsan
manual #306345
allowed to fail manual
ubsan
 
  Review
manual #306349
allowed to fail manual
review
manual #306350
allowed to fail manual
stop_review