chore: update pdfpig nuget package version by filzrev · Pull Request #9803 · dotnet/docfx

This PR manually update pdfpig nuget package version.

PR #9800 failed with following errors.
Because latest version of pdfpig enables nullable annotations.

Possible null reference argument for parameter 'fileBytes' in 'PdfDocument PdfDocument.Open(byte[] fileBytes, ParsingOptions? options = null)'.

This PR intended to fix above issue by adding null check.