chore: bump actions/setup-python (#8)

Addressing the GHA message: 
```
Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/setup-python@v4. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.
```

action.yml

@@ -27,7 +27,7 @@ runs:
       run: echo "::add-mask::${{ inputs.token }}"
 
     - name: Setup Python 3
-      uses: actions/setup-python@v4
+      uses: actions/setup-python@v5
       if: ${{ inputs.setup-python == 'true' }}
       with:
         python-version: '3.x'
@@ -77,4 +77,4 @@ runs:
     - name: Validate the CLI is installed
       if: ${{ inputs.token != '' }}
       run: linode-cli --version
-      shell: bash
+      shell: bash