use multiple threads in integration tests (#4379)

substrate/.gitlab-ci.yml

@@ -202,7 +202,7 @@ test-linux-stable-int:
     - echo "___Logs will be partly shown at the end in case of failure.___"
     - echo "___Full log will be saved to the job artifacts only in case of failure.___"
     - WASM_BUILD_NO_COLOR=1 RUST_LOG=sync=trace,consensus=trace,client=trace,state-db=trace,db=trace,forks=trace,state_db=trace,storage_cache=trace
-        time cargo test -p node-cli --release --verbose --locked -- --ignored --test-threads=1
+        time cargo test -p node-cli --release --verbose --locked -- --ignored
         &> ${CI_COMMIT_SHORT_SHA}_int_failure.log
     - sccache -s
   after_script: