Push PDF pages rendering below full screen bar

[marcellamaki]

Summary

Updates the PDF renderer index so that the full screen bar does not cover the top of the first page of the PDF.

References

Fixes #8745

Reviewer guidance

Open a PDF in the content renderer.

Is this spacing okay, or should there be an additional scrolling/height calculation so the page moves up when the bar disappears?

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
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• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[nucleogenesis]

Browser test with pex passes - code lgtm!