Docs: Sentence case Secure section feature names

Problem to solve

For consistency, we should sentence case all the feature names under the 'Secure' section of the docs.

There's also quite a bit of mixed case in the UI, which we can iron out as we go.

Related items

• FY26Q3 Stage Lead planning issue: Application S... (gitlab-org/technical-writing/team-tasks#1398)

Checklist

To make it easier to chunk this work up, I'll open MRs according to how features are organized in the left navigation.

Here are the highlights, plus a few features that specifically need to be updated:

• Application security testing
• Compliance
• Detect
  • Container scanning
  • Container scanning for registry
  • Dependency scanning
  • Dependency list
  • Libbehave
  • Continuous vulnerability scanning
  • Static application security testing
  • Infrastructure as code scanning
  • Secret detection
  • Dynamic application security testing
  • API security
  • Web API fuzz testing
• Triage
• Analyze
• Remediate
• GitLab advisory database
• CVE ID requests
• Policies
• Security glossary

Don't forget to update the left navigation and the cards on secure your application.