stable35: include dependency updates required by LibreSign stable35

[vitormattos]

Context

LibreSign/libresign:stable35 currently references 3rdparty commit 9b2d970391b802245dc2bcf8ee384ccf44d70bf3, but the LibreSign/3rdparty:stable35 branch still points to cddfc39be9e5841421ffb954f919afc2ff6a9809.

This happened because the LibreSign stable35 backports reused commits from the 3rdparty main line instead of first advancing/backporting the corresponding dependency changes to 3rdparty:stable35:

• LibreSign #8260 (backport of #8256) moved the submodule from cddfc39 to 63d763a, the head commit of 3rdparty PR Update jsignpdf-php to v3.0.0 #96 (main).
• LibreSign #8263 (backport of #8255) then moved it from 63d763a to 9b2d970, the merge commit of 3rdparty PR chore: update pdf signature validator to 0.5.2 #97 (main).

A git submodule stores only a commit SHA, not a branch relationship, so Git allowed stable35 to reference those commits even though 3rdparty:stable35 had never been advanced.

What is between cddfc39 and 9b2d970

The range is a linear fast-forward of 9 commits containing four dependency updates and their merge commits:

1. 6f5ccab - update PDF signature validator to v0.5.0
2. c5f453b - merge 3rdparty Update PDF signature validator to v0.5.0 #94
3. f6966f7 - update PDF signature validator to v0.5.1
4. 4615d2b - merge 3rdparty chore(deps): update PDF signature validator to v0.5.1 #95
5. 097e30e - update jsignpdf-php to v3.0.0
6. 63d763a - regenerate scoped dependencies for jsignpdf-php 3
7. 40a9894 - merge 3rdparty Update jsignpdf-php to v3.0.0 #96
8. 804ba62 - update PDF signature validator to v0.5.2
9. 9b2d970 - merge 3rdparty chore: update pdf signature validator to 0.5.2 #97

These are the dependency-side changes required by the LibreSign stable35 backports #8260 and #8263. There are no unrelated later main changes in this range.

Change

Fast-forward 3rdparty:stable35 from cddfc39 to 9b2d970 so that the stable branch actually contains the dependency commits already consumed by LibreSign/libresign:stable35.

This does not introduce newer main changes such as GeoIP2 or jsignpdf-php 3.2.0; those are after 9b2d970.

Validation

• cddfc39...9b2d970 is a strict fast-forward: 9 ahead, 0 behind.
• The range contains only the PDF signature validator 0.5.x and jsignpdf-php 3.0.0 updates required by the corresponding LibreSign stable35 backports.
• LibreSign/libresign:stable35 already references 9b2d970.
• stable34 and stable33 remain on their own corresponding 3rdparty branches/commits.