.github/workflows: update Python build versions

Drop Python 3.8.
Add Python 3.13.

Drop macOS 12.
Add macOS 15.

Change-Id: I5916cf2de54dfb0274e50a8db3b8d93a60940710
Reviewed-on: https://code-review.googlesource.com/c/re2/+/63730
Reviewed-by: Alan Donovan <adonovan@google.com>
diff --git a/.github/workflows/python.yml b/.github/workflows/python.yml
index 57a5927..87e76a2 100644
--- a/.github/workflows/python.yml
+++ b/.github/workflows/python.yml
@@ -28,7 +28,7 @@
           - { name: X64,   python-name: x86_64,  runs-on: [ubuntu-latest]              }
           - { name: ARM64, python-name: aarch64, runs-on: [ubuntu-24.04-arm] }
         os: [manylinux_2_28]
-        ver: ['3.8', '3.9', '3.10', '3.11', '3.12']
+        ver: ['3.9', '3.10', '3.11', '3.12', '3.13']
     env:
       BAZELISK_GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       PYTHON: /usr/local/bin/python${{ matrix.ver }}
@@ -81,10 +81,10 @@
         arch:
           - { name: X64,   bazel-name: x86_64, python-name: x86_64 }
           - { name: ARM64, bazel-name: arm64,  python-name: arm64  }
-        # TODO(junyer): Stop cross-compiling after we drop support for macOS 12;
+        # TODO(rsc): Stop cross-compiling now that we don't use macOS 12.
         # instead, specify `-large` suffix on X64 and `-xlarge` suffix on ARM64.
-        os: [12, 13, 14]
-        ver: ['3.8', '3.9', '3.10', '3.11', '3.12']
+        os: [13, 14, 15]
+        ver: ['3.9', '3.10', '3.11', '3.12', '3.13']
     env:
       BAZELISK_GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       BAZEL_CPU: darwin_${{ matrix.arch.bazel-name }}
@@ -146,7 +146,7 @@
         arch:
           - { name: X86, bazel-name: x64_x86, python-name: win32     }
           - { name: X64, bazel-name: x64,     python-name: win_amd64 }
-        ver: ['3.8', '3.9', '3.10', '3.11', '3.12']
+        ver: ['3.9', '3.10', '3.11', '3.12', '3.13']
     env:
       BAZELISK_GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       BAZEL_CPU: ${{ matrix.arch.bazel-name }}_windows