build: bump pypdf from 6.6.2 to 6.8.0 in /infra/scripts/index_scripts

Bumps [pypdf](https://github.com/py-pdf/pypdf) from 6.6.2 to 6.8.0.
- [Release notes](https://github.com/py-pdf/pypdf/releases)
- [Changelog](https://github.com/py-pdf/pypdf/blob/main/CHANGELOG.md)
- [Commits](py-pdf/pypdf@6.6.2...6.8.0)

---
updated-dependencies:
- dependency-name: pypdf
  dependency-version: 6.8.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

infra/scripts/index_scripts/requirements.txt

@@ -5,7 +5,7 @@ azure-ai-agents==1.2.0b5
 azure-ai-inference==1.0.0b9
 agent-framework-core==1.0.0rc2
 agent-framework-azure-ai==1.0.0rc2
-pypdf==6.6.2
+pypdf==6.8.0
 tiktoken==0.12.0
 azure-identity==1.25.2
 azure-ai-textanalytics==5.3.0