ci: don't create xvfb for unit_test (#34007)

no more

.github/workflows/selfdrive_tests.yaml

@@ -176,8 +176,7 @@ jobs:
     - name: Run unit tests
       timeout-minutes: ${{ contains(runner.name, 'nsc') && 1 || 20 }}
       run: |
-        ${{ env.RUN }} "source selfdrive/test/setup_xvfb.sh && \
+        ${{ env.RUN }} "MAX_EXAMPLES=1 $PYTEST --timeout 60 -m 'not slow' && \
-                        MAX_EXAMPLES=1 $PYTEST --timeout 60 -m 'not slow' && \
                         ./selfdrive/ui/tests/create_test_translations.sh && \
                         QT_QPA_PLATFORM=offscreen ./selfdrive/ui/tests/test_translations"
     - name: "Upload coverage to Codecov"