Fix list in sol arch docs

This MR Template ensures that Solutions Docs published here: https://docs.gitlab.com/ee/solutions/, follow the optimized review and approval workflow for that area rather than the normal tech writing workflow by applying appropriate labels and reviewers.

What does this MR do?

Fixes a list on the root page.

Related issues

Review

• I have read the Solutions Docs Contributors Guide in the GitLab Handbook and believe that this contribution complies with the scope and requirements outlined there.
• Assign yourself as the Assignee of this MR.
• Assign the latest release for the Milestone. If you're not sure, view the list of releases.
• Mention the reviewers in a comment, so they're aware that the MR is ready.

Merging

• Obtain approval from a member of the Solutions Documentation Approvers Group (CODEOWNERS for the Solutions directory)

When a code owner approves, they can merge.

Troubleshooting

The pipeline will test for style and link issues. If you have issues you're unable to resolve, view the documentation Style Guide or ask for assistance in the #docs Slack channel.