Fix wrong generation of aria-labelledby in tab navigation

[janbensch]

Fixes wrong autogeneration of aria-labelledby in tab navigation.
Fixes #38222

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Related issues

Fixes #38222

[XhmikosR]

Thanks for the PR! Good catch, because the test was also wrong so it was harder to spot.

For future reference it seems this was broken in 135b9cd#diff-6090db9da36e79f2e879e6d5232960d82d60af6017a0297d6c500c7cdb5953a1R221

[janbensch]

Thanks for the quick approval. And sorry that I missed the test case!