Card sizing for security dashboard discovery moment experiment

What does this MR do and why?

Card sizing for security dashboard discovery moment experiment

Related to #365499

Screenshots or screen recordings

Before	After Large	After Medium	After Small

How to set up and validate locally

1. Act like SAAS https://docs.gitlab.com/ee/development/ee_features.html#act-as-saas
2. Enable the experiment flag bin/rails c => Feature.enable(:showcase_free_security_features)
3. Create a group GROUP and a project PROJECT
4. Go to the Security tab of the group and of the project

• http://gdk.test:3000/groups/GROUP/-/security/discover
• http://gdk.test:3000/GROUP/PROJECT/-/security/discover

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

.gitlab/ci/rules.gitlab-ci.yml

@@ -49,6 +49,9 @@
 .if-merge-request-targeting-stable-branch: &if-merge-request-targeting-stable-branch
   if: '$CI_MERGE_REQUEST_IID && $CI_MERGE_REQUEST_TARGET_BRANCH_NAME =~ /^[\d-]+-stable(-ee)?$/'
 
+.if-merge-request-labels-run-in-ruby3: &if-merge-request-labels-run-in-ruby3
+  if: '$CI_MERGE_REQUEST_LABELS =~ /pipeline:run-in-ruby3/'
+
 .if-merge-request-labels-as-if-foss: &if-merge-request-labels-as-if-foss
   if: '$CI_MERGE_REQUEST_LABELS =~ /pipeline:run-as-if-foss/'
 
@@ -1789,6 +1792,10 @@
     - <<: *if-default-refs
       changes: *code-backstage-patterns
 
+.setup:rules:verify-ruby-2.7:
+  rules:
+    - <<: *if-merge-request-labels-run-in-ruby3
+
 .setup:rules:verify-tests-yml:
   rules:
     - <<: *if-not-ee