gitlab-ci: Allow flatpak build to fail

This works around infrastructure failure.
11 jobs for flatpak-fail in 21 minutes and 47 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #241984
librem5
api-visibility

00:02:11

passed #241986
librem5
build-debian-clang

00:03:21

passed #241985
librem5
build-debian-gcc

00:02:30

passed #241987
librem5
build-fedora-gcc

00:02:47

 
  Test+Docs
passed #241988
librem5
build-gtkdoc

00:02:46

passed #241989
librem5
unit-test

00:02:46

43.7%
 
  Package
passed #241990
librem5
package-debian-buster

00:02:46

passed #241991
librem5:arm64
package-debian-buster:arm64

00:07:26

failed #241992
flatpak allowed to fail
package-flatpak

00:01:07

 
  Test Package
passed #241993
librem5
autopkgtest-debian-buster-package

00:02:35

passed #241994
librem5
lintian-debian-buster-package

00:00:55

 
Name Stage Failure
failed
package-flatpak Package
Committing stage finish to cache
Exporting sm.puri.Handy.Demo to repo
error: Writing content object: min-free-space-percent '3%' would be exceeded, at least 4.1?kB requested
Export failed: Child process exited with code 1
Uploading artifacts...
_build/meson-logs/meson-log.txt: found 1 matching files
WARNING: sm.puri.Handy.Demo-dev.flatpak: no matching files
Uploading artifacts to coordinator... ok
id=241992 responseStatus=201 Created token=FLQT8upa
ERROR: Job failed: exit code 1