Prepare release v0.8.4 (#190)

## heroku/python

### Changed

- Updated the default Python version from 3.12.2 to 3.12.3. ([#189](#189))

Co-authored-by: heroku-linguist[bot] <136119646+heroku-linguist[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.8.4] - 2024-04-09
+
 ### Changed
 
 - Updated the default Python version from 3.12.2 to 3.12.3. ([#189](https://github.com/heroku/buildpacks-python/pull/189))
@@ -115,7 +117,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Initial implementation. ([#3](https://github.com/heroku/buildpacks-python/pull/3))
 
-[unreleased]: https://github.com/heroku/buildpacks-python/compare/v0.8.3...HEAD
+[unreleased]: https://github.com/heroku/buildpacks-python/compare/v0.8.4...HEAD
+[0.8.4]: https://github.com/heroku/buildpacks-python/compare/v0.8.3...v0.8.4
 [0.8.3]: https://github.com/heroku/buildpacks-python/compare/v0.8.2...v0.8.3
 [0.8.2]: https://github.com/heroku/buildpacks-python/compare/v0.8.1...v0.8.2
 [0.8.1]: https://github.com/heroku/buildpacks-python/compare/v0.8.0...v0.8.1

buildpack.toml

@@ -2,7 +2,7 @@ api = "0.9"
 
 [buildpack]
 id = "heroku/python"
-version = "0.8.3"
+version = "0.8.4"
 name = "Heroku Python"
 homepage = "https://github.com/heroku/buildpacks-python"
 description = "Heroku's buildpack for Python applications."