.gitlab-ci.yml: Temporarily switch to Fedora rawhide

Since commit a34cb719, we need pixman >= 0.36, which is not yet
in the latest Fedora. Thus, this switches to Fedora rawhide to make
things work again.

Signed-off-by: Uli Schlachter <psychon@znc.in>
1 job for master in 12 minutes and 55 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #192457
fedora:test

00:12:55

 
Name Stage Failure
failed
fedora:test Test
make[1]: *** [Makefile:906: check-recursive] Error 1
make[1]: Leaving directory '/builds/cairo/cairo'
make: *** [Makefile:1358: check] Error 2
Uploading artifacts...
test/*.log: found 2 matching files
test/pdiff/*.log: found 1 matching files

test/output: found 2221 matching files

Uploading artifacts to coordinator... ok
id=192457 responseStatus=201 Created token=xjYEawyT
ERROR: Job failed: exit code 1