ARROW-8389: [Integration] Run tests in parallel

Now that Flight port binding has been fixed in ARROW-8176, we are able to run integration tests in parallel.

Closes #6888 from pitrou/ARROW-8389-integration-tests-parallel

Authored-by: Antoine Pitrou <antoine@python.org>
Signed-off-by: Neal Richardson <neal.p.richardson@gmail.com>

docker-compose.yml

@@ -1043,7 +1043,7 @@ services:
         /arrow/ci/scripts/java_build.sh /arrow /build &&
         /arrow/ci/scripts/js_build.sh /arrow /build &&
         pip install -e /arrow/dev/archery &&
-        archery integration --with-all --serial --run-flight"]
+        archery integration --with-all --run-flight"]
 
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