GH workflow: use actions/setup-python@v4

GitHub displays this warning with the actions/setup-python@2 :

Warning: The `set-output` command is deprecated and will be disabled soon.
Please upgrade to using Environment Files.
For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

.github/workflows/translations-update.yml

@@ -16,7 +16,7 @@ jobs:
         fetch-depth: '0'
         token: ${{ secrets.WEBLATE_GITHUB_TOKEN }}
     - name: Set up Python
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v4
       with:
         python-version: '3.9'
         architecture: 'x64'