ci: use FDO_CI_CONCURRENT if available to control the job count

7 jobs for wip/concurrent in 2 minutes and 41 seconds (queued for 13 seconds)
Status Name Job ID Coverage
  Container
passed container_fedora #15953814

00:00:24

passed container_ubuntu #15953816

00:00:19

 
  Build
passed build_on_fedora_no_docs #15953820

00:00:47

passed build_on_fedora_with_docs #15953818

00:00:43

passed build_on_ubuntu_no_gir #15953823

00:01:23

passed build_on_ubuntu_with_gir #15953821

00:00:48

 
  Analysis
passed shellcheck #15953825

00:00:19