CI: install_script: forward the pipeline ID instead of path to repo

This allows an easier split of the install script tests in 2 jobs in the
install-script CI.

.gitlab/install_script_testing.yml

@@ -9,11 +9,8 @@ test_install_script:
     - export GITLAB_TOKEN=$(aws ssm get-parameter --region us-east-1 --name ci.datadog-agent.gitlab_pipelines_scheduler_token --with-decryption --query "Parameter.Value" --out text)
     - export APT_URL=$DEB_TESTING_S3_BUCKET
     - export YUM_URL=$RPM_TESTING_S3_BUCKET
-    - export APT_REPO_VERSION_AGENT6="pipeline-$CI_PIPELINE_ID-a6-x86_64 6"
-    - export YUM_VERSION_PATH_AGENT6="testing/pipeline-$CI_PIPELINE_ID-a6/6"
-    - export APT_REPO_VERSION_AGENT7="pipeline-$CI_PIPELINE_ID-a7-x86_64 7"
-    - export YUM_VERSION_PATH_AGENT7="testing/pipeline-$CI_PIPELINE_ID-a7/7"
-    - inv pipeline.trigger-child-pipeline --project-name "DataDog/agent-linux-install-script" --git-ref "main" --variables "APT_URL,YUM_URL,APT_REPO_VERSION_AGENT6,APT_REPO_VERSION_AGENT7,YUM_VERSION_PATH_AGENT6,YUM_VERSION_PATH_AGENT7"
+    - export TEST_PIPELINE_ID=$CI_PIPELINE_ID
+    - inv pipeline.trigger-child-pipeline --project-name "DataDog/agent-linux-install-script" --git-ref "main" --variables "APT_URL,YUM_URL,TEST_PIPELINE_ID"
   needs: ["deploy_deb_testing-a6_x64", "deploy_rpm_testing-a6_x64", "deploy_deb_testing-a7_x64", "deploy_rpm_testing-a7_x64"]
   rules:
     !reference [.on_deploy]