Unify location for defining default Fedora image

.gitlab-ci.yml

@@ -3,9 +3,12 @@ stages:
   - test
   - report
 
+variables:
+  DEFAULT_FEDORA_IMAGE: registry.gitlab.com/kicad/kicad-ci/source_containers/master/fedora:40
+
 default:
   image:
-    name: registry.gitlab.com/kicad/kicad-ci/source_containers/master/fedora:36
+    name: $DEFAULT_FEDORA_IMAGE
     entrypoint: ["/bin/sh", "-c"]
 
 include:

.gitlab/Fedora-Linux-CI.yml

@@ -6,7 +6,7 @@
 # Don't tag until we have separate CI for MRs
 #  tags:
 #    - kicad-fedora
-  image: registry.gitlab.com/kicad/kicad-ci/source_containers/master/fedora:40
+  image: $DEFAULT_FEDORA_IMAGE
   extends: .only_code
   interruptible: false
   cache:
@@ -144,7 +144,7 @@ fedora_report_metrics_public:
 # Run the code unit tests.
 ##########################################################################
 .fedora_qa:
-  image: registry.gitlab.com/kicad/kicad-ci/source_containers/master/fedora:38
+  image: $DEFAULT_FEDORA_IMAGE
   extends:
     - .unit_test
     - .only_code

.gitlab/linux-metadata-validate.yml

@@ -5,8 +5,7 @@ validate_linux_metadata:
   stage: test
   needs: []
   interruptible: false
-  # This is the only CI image with the utilities needed for this test
+  image: $DEFAULT_FEDORA_IMAGE
-  image: registry.gitlab.com/kicad/kicad-ci/source_containers/master/fedora:40
   # Due to bug https://github.com/hughsie/appstream-glib/issues/381, this doesn't think our description tag
   # is localized even though it actually is.
   allow_failure: true