build(deps): bump asyncpg from 0.30.0 to 0.31.0 in /backend

Bumps [asyncpg](https://github.com/MagicStack/asyncpg) from 0.30.0 to 0.31.0.
- [Release notes](https://github.com/MagicStack/asyncpg/releases)
- [Commits](MagicStack/asyncpg@v0.30.0...v0.31.0)

---
updated-dependencies:
- dependency-name: asyncpg
  dependency-version: 0.31.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]