Bump pypdf from 3.17.0 to 6.4.0 in /ai/python-rag-chatbot

Bumps [pypdf](https://github.com/py-pdf/pypdf) from 3.17.0 to 6.4.0.
- [Release notes](https://github.com/py-pdf/pypdf/releases)
- [Changelog](https://github.com/py-pdf/pypdf/blob/main/CHANGELOG.md)
- [Commits](py-pdf/pypdf@3.17.0...6.4.0)

---
updated-dependencies:
- dependency-name: pypdf
  dependency-version: 6.4.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

ai/python-rag-chatbot/requirements.txt

@@ -174,7 +174,7 @@ pydeck==                                   0.8.1b0
 Pygments==                                 2.16.1
 pyOpenSSL==                                23.2.0
 pyparsing==                                3.1.2
-pypdf==                                    3.17.0
+pypdf== 6.4.0
 PyPika==                                   0.48.9
 pyproject_hooks==                          1.1.0
 pyproject-toml==                           0.0.10