Upgrade OSX CI environment.

Author: stefanseefeld

.github/workflows/test-osx.yml

@@ -9,14 +9,14 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.6]
+        python-version: [3.10]
         cxx: [clang++]
         std: [c++98, c++11, c++14] # TODO: c++17 is failing !
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: setup python
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
     - name: setup prerequisites