refactor: single hcloud_token var definition and remove parallel exec in ci

Signed-off-by: Vojtěch Mareš <vojtech@mares.cz>

.gitlab-ci.yml

@@ -14,13 +14,6 @@ stages:
   - validate
   - build
 
-.parallel:
-  parallel:
-    matrix:
-      - IMAGE:
-        - flatcar-stable
-        - talos-v1.10.3
-
 validate:
   stage: validate
   script:
@@ -28,10 +21,9 @@ validate:
     - packer fmt -check images
     - packer validate images
 
-build-image:
-  extends: .parallel
+build-images:
   stage: build
   script:
-    - packer build $IMAGE.pkr.hcl
+    - packer build images
   rules:
     - if: $CI_COMMIT_BRANCH == "main"