Bump the python-packages group in /backend with 2 updates

Bumps the python-packages group in /backend with 2 updates: [nltk](https://github.com/nltk/nltk) and [testcontainers[postgres]](https://github.com/testcontainers/testcontainers-python).


Updates `nltk` from 3.8.2 to 3.9.1
- [Changelog](https://github.com/nltk/nltk/blob/develop/ChangeLog)
- [Commits](nltk/nltk@3.8.2...3.9.1)

Updates `testcontainers[postgres]` from 4.7.2 to 4.8.0
- [Release notes](https://github.com/testcontainers/testcontainers-python/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-python/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-python@testcontainers-v4.7.2...testcontainers-v4.8.0)

---
updated-dependencies:
- dependency-name: nltk
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: python-packages
- dependency-name: testcontainers[postgres]
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: python-packages
...

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

backend/requirements.txt

@@ -5,7 +5,7 @@ pylint==3.2.6
 SQLAlchemy==2.0.32
 price-parser==0.3.4
 Scrapy==2.11.2
-nltk==3.8.2
+nltk==3.9.1
 Flask==3.0.3
 Flask-Cors==4.0.1
 Flask-Headers==1.0

backend/tests/requirements.txt

@@ -1,5 +1,5 @@
 ddt==1.7.2
 psycopg==3.2.1
 pytest==8.3.2
-testcontainers[postgres]==4.7.2
+testcontainers[postgres]==4.8.0
 unittest-xml-reporting==3.2.0