ci: remove macos-13 from GHA workflow

GitHub announcement:
The macOS 13 runner image will be retired by December 4th, 2025

Author: ralphlange

.github/workflows/build-and-test.yml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-24.04, ubuntu-22.04, windows-2025, windows-2022, macos-15, macos-14, macos-13]
+        os: [ubuntu-24.04, ubuntu-22.04, windows-2025, windows-2022, macos-15, macos-14]
     steps:
     - uses: actions/checkout@v4
     - name: Show initial environment
@@ -59,7 +59,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [macos-15, macos-14, macos-13]
+        os: [macos-15, macos-14]
         cmp: [clang]
         configuration: [default, debug]
     steps: