CI: update runner images

Closes #36.

Signed-off-by: Matthias Geier <705404+mgeier@users.noreply.github.com>

Author: mgeier

.github/workflows/tests.yml

@@ -10,7 +10,7 @@ jobs:
   test-bot:
     strategy:
       matrix:
-        os: [ubuntu-22.04, macos-13, macos-14]
+        os: [ubuntu-24.04, macos-13, macos-14, macos-15]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Set up Homebrew