Bump asyncpg from 0.27.0 to 0.28.0

Bumps [asyncpg](https://github.com/MagicStack/asyncpg) from 0.27.0 to 0.28.0.
- [Release notes](https://github.com/MagicStack/asyncpg/releases)
- [Commits](MagicStack/asyncpg@v0.27.0...v0.28.0)

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

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