Python: fix ollama integration test (microsoft#8364)

### Motivation and Context

<!-- Thank you for your contribution to the semantic-kernel repo!
Please help reviewers and future users, providing the following
information:
  1. Why is this change required?
  2. What problem does it solve?
  3. What scenario does it contribute to?
  4. If it fixes an open issue, please link to the issue here.
-->

### Description

<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

.github/workflows/python-integration-tests.yml

@@ -207,29 +207,28 @@ jobs:
       - name: Install Ollama
         if: matrix.os == 'ubuntu-latest'
         run: |
-          curl -fsSL https://ollama.com/install.sh | sh
-          ollama serve &
-          sleep 5
-
+          if ${{ vars.OLLAMA_MODEL != '' }}; then
+            curl -fsSL https://ollama.com/install.sh | sh
+            ollama serve &
+            sleep 5
+          fi
       - name: Pull model in Ollama
         if: matrix.os == 'ubuntu-latest'
         run: |
-          ollama pull ${{ vars.OLLAMA_MODEL }}
-          ollama list
-
+          if ${{ vars.OLLAMA_MODEL != '' }}; then
+            ollama pull ${{ vars.OLLAMA_MODEL }}
+            ollama list
+          fi
       - name: Google auth
         uses: google-github-actions/auth@v2
         with:
           project_id: ${{ vars.VERTEX_AI_PROJECT_ID }}
           credentials_json: ${{ secrets.VERTEX_AI_SERVICE_ACCOUNT_KEY }}
-
       - name: Set up gcloud
-        uses: google-github-actions/setup-gcloud@v2
-
+        uses: google-github-actions/setup-gcloud@v2      
       - name: Setup Redis Stack Server
         if: matrix.os == 'ubuntu-latest'
         run: docker run -d --name redis-stack-server -p 6379:6379 redis/redis-stack-server:latest
-
       - name: Run Integration Tests
         id: run_tests
         shell: bash