Bump astroid from 3.1.0 to 3.2.0 in /backend

Bumps [astroid](https://github.com/pylint-dev/astroid) from 3.1.0 to 3.2.0.
- [Release notes](https://github.com/pylint-dev/astroid/releases)
- [Changelog](https://github.com/pylint-dev/astroid/blob/main/ChangeLog)
- [Commits](pylint-dev/astroid@v3.1.0...v3.2.0)

---
updated-dependencies:
- dependency-name: astroid
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

backend/requirements.txt

@@ -1,4 +1,4 @@
-astroid==3.1.0
+astroid==3.2.0
 black==24.4.2
 click==8.1.7
 dill==0.3.8