tools: drop deprecated macos-13 runner

Refs: actions/runner-images#13046

Author: richardlau

.github/workflows/test-macos.yml

@@ -38,11 +38,7 @@ permissions:
 jobs:
   test-macOS:
     if: github.event.pull_request.draft == false
-    strategy:
-      fail-fast: false
-      matrix:
-        macos-version: [macos-13, macos-14]
-    runs-on: ${{ matrix.macos-version }}
+    runs-on: macos-14
     env:
       CC: sccache gcc
       CXX: sccache g++