github: test: retire macos-13

This runner is going to go away soon, drop it.

Link: https://github.blog/changelog/2025-09-19-github-actions-macos-13-runner-image-is-closing-down/
Signed-off-by: Fabio Baltieri <[email protected]>

Author: fabiobaltieri

.github/workflows/test.yaml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-24.04, ubuntu-24.04-arm, macos-13, macos-14, macos-15, windows-2022]
+        os: [ubuntu-24.04, ubuntu-24.04-arm, macos-14, macos-15, windows-2022]
         release: [v3.7.0, v4.1.0, v4.2.0, main]
     runs-on: ${{ matrix.os }}
     steps: