.gitlab-ci.yml: Use promtool from paritytech/tools:latest image (#6425)

substrate/.gitlab-ci.yml

@@ -364,10 +364,8 @@ test-prometheus-alerting-rules:
   image:                           paritytech/tools:latest
   <<:                              *kubernetes-build
   script:
-    - curl -L https://github.com/prometheus/prometheus/releases/download/v2.19.0/prometheus-2.19.0.linux-amd64.tar.gz --output prometheus.tar.gz
-    - tar -xzf prometheus.tar.gz
-    - ./prometheus-*/promtool check rules .maintain/monitoring/alerting-rules/alerting-rules.yaml
-    - cat .maintain/monitoring/alerting-rules/alerting-rules.yaml | ./prometheus-*/promtool test rules .maintain/monitoring/alerting-rules/alerting-rule-tests.yaml
+    - promtool check rules .maintain/monitoring/alerting-rules/alerting-rules.yaml
+    - cat .maintain/monitoring/alerting-rules/alerting-rules.yaml | promtool test rules .maintain/monitoring/alerting-rules/alerting-rule-tests.yaml
 
 #### stage:                        build