Set python version for addon-checker to 3.12

Author: goggle

.github/workflows/addoncheck-matrix.yml

@@ -12,7 +12,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v5
       with:
-        python-version: '3.x'
+        python-version: '3.12'
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip

.github/workflows/addoncheck-nexus.yml

@@ -12,7 +12,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v5
       with:
-        python-version: '3.x'
+        python-version: '3.12'
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip

.github/workflows/addoncheck-omega.yml

@@ -12,7 +12,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v5
       with:
-        python-version: '3.x'
+        python-version: '3.12'
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip