Update databases[postgresql] requirement

Updates the requirements on [databases[postgresql]](https://github.com/encode/databases) to permit the latest version.
- [Release notes](https://github.com/encode/databases/releases)
- [Changelog](https://github.com/encode/databases/blob/master/CHANGELOG.md)
- [Commits](https://github.com/encode/databases/compare/0.3.2...0.5.1)

---
updated-dependencies:
- dependency-name: databases[postgresql]
  dependency-type: direct:production
...

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

requirements.txt

@@ -1,4 +1,4 @@
-databases[sqlite]>=0.3.2,<0.5.1
+databases[sqlite]>=0.3.2,<0.5.2
 databases[postgresql]>=0.3.2,<0.5.1
 databases[mysql]>=0.3.2,<0.5.1
 pydantic >=1.6.1,!=1.7,!=1.7.1,!=1.7.2,!=1.7.3,!=1.8,!=1.8.1,<=1.8.2