ci: skip non-windows tests; the flaky test failure we're investigatin…

…g only occurs on windows

Ref: sphinx-doc#11232

.github/workflows/main.yml

@@ -16,53 +16,6 @@ env:
   PYTHONWARNINGS: "error"  # default: all warnings as errors
 
 jobs:
-  ubuntu:
-    runs-on: ubuntu-latest
-    name: Python ${{ matrix.python }} (Docutils ${{ matrix.docutils }})
-    strategy:
-      fail-fast: false
-      matrix:
-        python:
-        - "3.9"
-        - "3.10"
-        - "3.11"
-        - "3.12-dev"
-        - "3.13-dev"
-        docutils:
-        - "0.18"
-        - "0.19"
-        - "0.20"
-
-    steps:
-    - uses: actions/checkout@v3
-    - name: Set up Python ${{ matrix.python }}
-      uses: actions/setup-python@v4
-      if: "!endsWith(matrix.python, '-dev')"
-      with:
-        python-version: ${{ matrix.python }}
-    - name: Set up Python ${{ matrix.python }} (deadsnakes)
-      uses: deadsnakes/action@v2.1.1
-      if: "endsWith(matrix.python, '-dev')"
-      with:
-        python-version: ${{ matrix.python }}
-      env:
-        PYTHONWARNINGS: ""
-    - name: Check Python version
-      run: python --version
-    - name: Install graphviz
-      run: sudo apt-get install graphviz
-    - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install .[test]
-      env:
-        PYTHONWARNINGS: ""
-    - name: Install Docutils ${{ matrix.docutils }}
-      run: python -m pip install --upgrade "docutils~=${{ matrix.docutils }}.0"
-      env:
-        PYTHONWARNINGS: ""
-    - name: Test with pytest
-      run: python -m pytest -vv --durations 25
 
   windows:
     runs-on: windows-2019
@@ -82,30 +35,3 @@ jobs:
         PYTHONWARNINGS: ""
     - name: Test with pytest
       run: python -m pytest -vv --durations 25
-
-  docutils-latest:
-    runs-on: ubuntu-latest
-    name: Docutils HEAD
-
-    steps:
-    - uses: actions/checkout@v3
-    - name: Set up Python 3
-      uses: actions/setup-python@v4
-      with:
-        python-version: "3"
-    - name: Check Python version
-      run: python --version
-    - name: Install graphviz
-      run: sudo apt-get install graphviz
-    - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install .[test]
-      env:
-        PYTHONWARNINGS: ""
-    - name: Install Docutils' HEAD
-      run: python -m pip install git+https://repo.or.cz/docutils.git\#subdirectory=docutils
-      env:
-        PYTHONWARNINGS: ""
-    - name: Test with pytest
-      run: python -m pytest -vv