Add support for Python 3.11.7 and 3.12.1 (#154)

Announcement:
https://blog.python.org/2023/12/python-3121-is-now-available.html

Release notes:
https://www.python.org/downloads/release/python-3117/
https://www.python.org/downloads/release/python-3121/
https://docs.python.org/release/3.11.7/whatsnew/changelog.html#python-3-11-7
https://docs.python.org/release/3.12.1/whatsnew/changelog.html#python-3-12-1-final

Binary builds:
https://github.com/heroku/heroku-buildpack-python/actions/runs/7106875936
https://github.com/heroku/heroku-buildpack-python/actions/runs/7138923192

GUS-W-12345430.
GUS-W-14233002.

CHANGELOG.md

@@ -9,7 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
-- Changed the default Python version from 3.11 to 3.12. ([#152](https://github.com/heroku/buildpacks-python/pull/152))
+- Updated the default Python version from 3.11.6 to 3.12.1. ([#152](https://github.com/heroku/buildpacks-python/pull/152) and [#154](https://github.com/heroku/buildpacks-python/pull/154))
 - Updated wheel from 0.41.3 to 0.42.0. ([#150](https://github.com/heroku/buildpacks-python/pull/150))
 
 ## [0.7.3] - 2023-11-06

src/python_version.rs

@@ -9,7 +9,7 @@ use std::path::Path;
 pub(crate) const DEFAULT_PYTHON_VERSION: PythonVersion = PythonVersion {
     major: 3,
     minor: 12,
-    patch: 0,
+    patch: 1,
 };
 
 /// Representation of a specific Python `X.Y.Z` version.

tests/fixtures/python_3.11/runtime.txt

@@ -1 +1 @@
-python-3.11.6
+python-3.11.7

tests/fixtures/python_3.12/runtime.txt

@@ -1 +1 @@
-python-3.12.0
+python-3.12.1

tests/mod.rs

@@ -15,8 +15,8 @@ const LATEST_PYTHON_3_7: &str = "3.7.17";
 const LATEST_PYTHON_3_8: &str = "3.8.18";
 const LATEST_PYTHON_3_9: &str = "3.9.18";
 const LATEST_PYTHON_3_10: &str = "3.10.13";
-const LATEST_PYTHON_3_11: &str = "3.11.6";
-const LATEST_PYTHON_3_12: &str = "3.12.0";
+const LATEST_PYTHON_3_11: &str = "3.11.7";
+const LATEST_PYTHON_3_12: &str = "3.12.1";
 const DEFAULT_PYTHON_VERSION: &str = LATEST_PYTHON_3_12;
 
 const DEFAULT_BUILDER: &str = "heroku/builder:22";