Upgrade pypdf (#2799)

Author: pamelafox

app/backend/requirements.txt

@@ -349,7 +349,7 @@ pyjwt==2.10.1
     #   msal
 pymupdf==1.26.0
     # via -r requirements.in
-pypdf==6.0.0
+pypdf==6.1.3
     # via -r requirements.in
 python-dotenv==1.1.1
     # via
@@ -422,6 +422,7 @@ typing-extensions==4.13.2
     #   azure-storage-file-datalake
     #   exceptiongroup
     #   hypercorn
+    #   multidict
     #   openai
     #   opentelemetry-api
     #   opentelemetry-sdk