ci: make "trigger-build-of-testing-image" job use the same rules as "release" job

.gitlab-ci.yml

@@ -5,8 +5,7 @@ stages:
 
 trigger-build-of-testing-image:
   needs:
-    - job: release
-      optional: true
+    - release
   stage: release
   image: curlimages/curl
   variables:
@@ -14,4 +13,6 @@ trigger-build-of-testing-image:
   script:
     - if [ ! -f $RELEASED_VERSION_ARTIFACT ]; then echo "No version released, exiting..."; exit; fi
     - RELEASED_MAJOR_VERSION=$(cut -d. -f1 $RELEASED_VERSION_ARTIFACT)
-    - curl --fail-with-body --request POST --form "token=$CI_JOB_TOKEN" --form ref=ci-workflow --form "variables[IMAGE_TYPE]=testing" --form "variables[QUIQQER_VERSION]=$RELEASED_MAJOR_VERSION" "$CI_API_V4_URL/projects/835/trigger/pipeline"
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+    - curl --fail-with-body --request POST --form "token=$CI_JOB_TOKEN" --form ref=ci-workflow --form "variables[IMAGE_TYPE]=testing" --form "variables[QUIQQER_VERSION]=$RELEASED_MAJOR_VERSION" "$CI_API_V4_URL/projects/835/trigger/pipeline"
+  rules:
+    - !reference [release, rules]
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