python: do not build for macOS13, add macos15

https://github.blog/changelog/2025-09-19-github-actions-macos-13-runner-image-is-closing-down/

Signed-off-by: Tristram Gräbener <tristram+git@tristramg.eu>

Author: Tristramg

.github/workflows/publish_pypi.yaml

@@ -141,10 +141,10 @@ jobs:
     strategy:
       matrix:
         platform:
-          - runner: macos-13
-            target: x86_64
           - runner: macos-14
             target: aarch64
+          - runner: macos-15
+            target: aarch64
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5