ci: workflow: update macOS runner from macos-13 to macos-15

Replace deprecated macos-13 with macos-15 in build matrix to ensure
compatibility with supported GitHub Actions runners.

Signed-off-by: Leif Harald Urlaub <[email protected]>

Author: leur-nordic

.github/workflows/hello_world_multiplatform.yaml

@@ -28,7 +28,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-22.04, ubuntu-24.04, macos-13, macos-14, windows-2022]
+        os: [ubuntu-22.04, ubuntu-24.04, macos-15, macos-14, windows-2022]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout
@@ -82,4 +82,4 @@ jobs:
           if-no-files-found: ignore
           path:
             zephyr/twister-out/*/samples/hello_world/sample.basic.helloworld/build.log
-            zephyr/twister-out/*/samples/cpp/hello_world/sample.cpp.helloworld/build.log
+            zephyr/twister-out/*/samples/cpp/hello_world/sample.cpp.helloworld/build.log