Bump postgrex from 0.19.0 to 0.19.1 (#318)

Bumps [postgrex](https://github.com/elixir-ecto/postgrex) from 0.19.0 to 0.19.1.
- [Release notes](https://github.com/elixir-ecto/postgrex/releases)
- [Changelog](https://github.com/elixir-ecto/postgrex/blob/master/CHANGELOG.md)
- [Commits](elixir-ecto/postgrex@v0.19.0...v0.19.1)

---
updated-dependencies:
- dependency-name: postgrex
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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