Update Assimp to fix compilation with gcc 13

[benjaminum]

Type

• [X] Bug fix (non-breaking change which fixes an issue): Fixes #
• [ ] New feature (non-breaking change which adds functionality). Resolves #
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected) Resolves #

Motivation and Context

Checklist:

• [ ] I have run python util/check_style.py --apply to apply Open3D code style to my code.
• [ ] This PR changes Open3D behavior or adds new functionality.
  • [ ] Both C++ (Doxygen) and Python (Sphinx / Google style) documentation is updated accordingly.
  • [ ] I have added or updated C++ and / or Python unit tests OR included test results (e.g. screenshots or numbers) here.
• [ ] I will follow up and update the code if CI fails.
• [ ] For fork PRs, I have selected Allow edits from maintainers.

Description

Update to latest main for assimp (>5.4.1) to fix a compilation issue with GCC 13 (See https://github.com/assimp/assimp/issues/5592). Resolves the Assimp problem in #6544

[update-docs[bot]]

Thanks for submitting this pull request! The maintainers of this repository would appreciate if you could update the CHANGELOG.md based on your changes.

[ssheorey]

Check Ubuntu 18.04 / 20.04 errors.