Bump pikepdf from 9.2.0 to 9.2.1 in /docker/readpdf (#31410)

Bumps [pikepdf](https://github.com/pikepdf/pikepdf) from 9.2.0 to 9.2.1.
- [Release notes](https://github.com/pikepdf/pikepdf/releases)
- [Commits](pikepdf/pikepdf@v9.2.0...v9.2.1)

---
updated-dependencies:
- dependency-name: pikepdf
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>