bump up actions/checkout from @v4 to @v5 in validation.yml

Author: WolfgangWaltenberger

.github/workflows/validation.yml

@@ -25,7 +25,7 @@ jobs:
         os: [ubuntu-22.04, ubuntu-24.04, macos-13, macos-14, macos-15 ]
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
       with:

smodels/version

@@ -1 +1 @@
-3.1.0
+3.1.1-rc1