chore(deps): update duckduckgo-search requirement in /backend

Updates the requirements on [duckduckgo-search](https://github.com/deedy5/duckduckgo_search) to permit the latest version.
- [Release notes](https://github.com/deedy5/duckduckgo_search/releases)
- [Commits](https://github.com/deedy5/duckduckgo_search/compare/v6.2.12...v6.2.13)

---
updated-dependencies:
- dependency-name: duckduckgo-search
  dependency-type: direct:production
...

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

backend/requirements.txt

@@ -80,7 +80,7 @@ pytube==15.0.0
 
 extract_msg
 pydub
-duckduckgo-search~=6.2.11
+duckduckgo-search~=6.2.13
 
 ## Tests
 docker~=7.1.0