Fix attempt for launching with 4 threads

Author: Samuel-amap

.github/workflows/CI.yml

@@ -40,8 +40,8 @@ jobs:
       - uses: julia-actions/cache@v2
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
-        with: 
-          test_args: '--threads 4'
+        env:
+          JULIA_NUM_THREADS: 4
       - uses: julia-actions/julia-processcoverage@v1
       - uses: codecov/codecov-action@v5
         with: