Remove test-matrix references

Though other CASE repositories use a Python version matrix, this one
doesn't.  Defer to defaults.

Signed-off-by: Alex Nelson <alexander.nelson@nist.gov>

.github/workflows/web_resources.yml

@@ -30,10 +30,8 @@ jobs:
       with:
         distribution: 'temurin'
         java-version: '11'
-    - name: Set up Python ${{ matrix.python-version }}
+    - name: Set up Python
       uses: actions/setup-python@v5
-      with:
-        python-version: ${{ matrix.python-version }}
     - name: Pre-commit Checks
       run: |
         pip -q install pre-commit