automatically infer torch version for ci

.github/workflows/ci.yml

@@ -21,7 +21,6 @@ jobs:
       fail-fast: false
       matrix:
         python-version: ['3.9', '3.12']
-        torch-version: ['1.13']
 
     steps:
     - name: Checkout
@@ -40,15 +39,14 @@ jobs:
       uses: actions/cache@v4
       with:
         path: ~/.cache/pip
-        key: ${{ runner.os }}-pip-${{ matrix.python-version }}-${{ matrix.torch-version }}$
+        key: ${{ runner.os }}-pip-${{ matrix.python-version }}
         restore-keys: |
           ${{ runner.os }}-pip-${{ matrix.python-version }}-
           ${{ runner.os }}-pip-
 
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install torch==${{ matrix.torch-version }} --extra-index-url https://download.pytorch.org/whl/cpu
         pip install -e .[dev]
 
     - name: Run the fast CPU tests with coverage