Fix hyphenation in Cross-Functional Programs heading

Bob Singhrequested to merge
gitlab-community/gitlab-org/gitlab-runner:docs/fix-cross-functional into main

What does this MR do?

Fixes a minor wording issue in a section heading.

Why was this MR needed?

Improves consistency and correctness.

How to test

Review the diff and confirm the heading is correct.

Related issues

N/A

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