Update ci.yaml

Author: epenet

.github/workflows/ci.yaml

@@ -1338,8 +1338,8 @@ jobs:
           python3 -b -X dev -m pytest \
             -qq \
             --timeout=9 \
+            -n auto \
             ${cov_params[@]} \
-            -n 1 \
             -o console_output_style=count \
             --durations=0 \
             --durations-min=1 \