chore(toolchain): use the last build and add 3.15.0a1 (#3357)

Updating the toolchain versions to fix a bug in `3.13.8`. This will make
the release better to everyone.

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: aignas

CHANGELOG.md

@@ -83,12 +83,12 @@ END_UNRELEASED_TEMPLATE
   vendoring the `requirements.bzl` file, please re-vendor so that downstream is unaffected
   when the APIs get removed. If you need to customize the way the dependencies get
   evaluated, see [our docs](/pypi/download.html#customizing-requires-dist-resolution) on customizing `Requires-Dist` resolution.
-* (toolchains) Added Python versions 3.14.0, 3.13.8, 3.12.12, 3.11.14, 3.10.19, and 3.9.24
-  from the [20251010] release.
+* (toolchains) Added Python versions 3.15.0a1, 3.14.0, 3.13.9, 3.12.12, 3.11.14, 3.10.19, and 3.9.24
+  from the [20251014] release.
 * (deps) (bzlmod) Upgraded to `bazel-skylib` version
   [1.8.2](https://github.com/bazelbuild/bazel-skylib/releases/tag/1.8.2)
 
-[20251010]: https://github.com/astral-sh/python-build-standalone/releases/tag/20251010
+[20251014]: https://github.com/astral-sh/python-build-standalone/releases/tag/20251014
 
 {#v1-7-0-fixed}
 ### Fixed
@@ -1982,4 +1982,4 @@ Breaking changes:
 * (pip) Create all_data_requirements alias
 * Expose Python C headers through the toolchain.
 
-[0.24.0]: https://github.com/bazel-contrib/rules_python/releases/tag/0.24.0
+[0.24.0]: https://github.com/bazel-contrib/rules_python/releases/tag/0.24.0