Add RTL test to `@shared/GithubBuildShaLink.jsx`

[apburnes]

Add a test to @shared/GithubBuildShaLink.jsx using the RTL framework.

Acceptance Criteria

• [ ] Colocate test file to @shared/GithubBuildShaLink.test.jsx
• [ ] Test the GithubLink component renders with the build.clonedCommitSha prop
• [ ] Test the GithubLink component renders with the build.requestedCommitSha prop
• [ ] Test nothing renders when the build.requestedCommitSha and build.clonedCommitSha are not available