Python: Fix Python test coverage report workflow (#12261)

### Motivation and Context

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Our Python test coverage workflow has been failing due to a breaking in
the text format of the test coverage output:
MishaKav/pytest-coverage-comment#202.

### Description

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These notes will help understanding how your code works. Thanks! -->
This PR fixes the issue by switching to xml.

### Contribution Checklist

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

- [x] The code builds clean without any errors or warnings
- [x] 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
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

Author: TaoChenOSU

.github/workflows/python-test-coverage-report.yml

@@ -43,7 +43,7 @@ jobs:
         with:
           github-token: ${{ secrets.GH_ACTIONS_PR_WRITE }}
           issue-number: ${{ env.PR_NUMBER }}
-          pytest-coverage-path: python/python-coverage.txt
+          pytest-xml-coverage-path: python/python-coverage.xml
           title: "Python Test Coverage Report"
           badge-title: "Python Test Coverage"
           junitxml-title: "Python Unit Test Overview"

.github/workflows/python-test-coverage.yml

@@ -36,12 +36,12 @@ jobs:
       - name: Install the project
         run: uv sync --all-extras --dev
       - name: Test with pytest
-        run: uv run --frozen pytest -q --junitxml=pytest.xml --cov=semantic_kernel --cov-report=term-missing:skip-covered ./tests/unit | tee python-coverage.txt
+        run: uv run --frozen pytest -q --junitxml=pytest.xml --cov=semantic_kernel --cov-report=term-missing:skip-covered --cov-report=xml:python-coverage.xml ./tests/unit
       - name: Upload coverage report
         uses: actions/upload-artifact@v4
         with:
           path: |
-            python/python-coverage.txt
+            python/python-coverage.xml
             python/pytest.xml
             python/pr_number
           overwrite: true