Update gha versions

Author: pgleeson

.github/workflows/omv-ci.yml

@@ -19,9 +19,9 @@ jobs:
         engine: [ NetPyNE, jNeuroML, jNeuroML_NEURON, jNeuroML_NetPyNE, jNeuroML_EDEN, jNeuroML_validate ]
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Set up Python  ${{ matrix.python-version }}
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version:  ${{ matrix.python-version }}