gitlab CI: move the pages job configuration to config.yml

Makes it less error-prone to forgetful updates like 191913, I hope.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

.gitlab-ci/ci.template

@@ -311,10 +311,10 @@ pages:
   stage: deploy
   extends:
     - .build@template
-    - .fdo.distribution-image@fedora
+    - .fdo.distribution-image@{{pages.distro}}
   variables:
-    FDO_DISTRIBUTION_VERSION: '35'
-    FDO_DISTRIBUTION_TAG: $FEDORA_TAG
+    FDO_DISTRIBUTION_VERSION: '{{pages.version}}'
+    FDO_DISTRIBUTION_TAG: ${{pages.distro.upper()}}_TAG
     MESON_ARGS: "-Ddocumentation=true"
   after_script:
     - mv "$MESON_BUILDDIR"/doc/html/ public

.gitlab-ci/config.yml

@@ -11,3 +11,7 @@ distributions:
     versions:
       - '35' # update the pages job when bumping the version
     use_for_custom_build_tests: true
+
+pages:
+  distro: fedora
+  version: 35