Flaky GUI test: `PDF viewer: fullscreen`

[touilleMan]

see https://github.com/Scille/parsec-cloud/actions/runs/25106514132/job/73569388595#step:12:594

  1) [Chromium] › tests/e2e/specs/file_viewers_pdf.spec.ts:312:3 › PDF viewer: fullscreen ──────────

    Error: expect(received).toBe(expected) // Object.is equality

    Expected: true
    Received: false

      326 |       return document.fullscreenElement !== null;
      327 |     });
    > 328 |     await expect(isFullScreen).toBe(true);
          |                                ^
      329 |   });
      330 | });
      331 |
        at /github/workspace/client/tests/e2e/specs/file_viewers_pdf.spec.ts:328:32

    Error Context: test-results/specs-file_viewers_pdf-PDF-viewer-fullscreen-Chromium/error-context.md