[integ-tests] Run trainium test on ubuntu2004

We changed the OS to alinux2023 and discovered the test requires some changes. To have the test passed, this commit changes back to ubuntu2004

Signed-off-by: Hanwen <hanwenli@amazon.com>

Author: hanwen-cluster

tests/integration-tests/configs/develop.yaml

@@ -738,7 +738,7 @@ test-suites:
       dimensions:
         - regions: ["usw2-az4"]  # do not move, unless instance type support is moved as well
           schedulers: ["slurm"]
-          oss: ["alinux2023"]
+          oss: ["ubuntu2004"]
   update:
     test_update.py::test_update_slurm:
       dimensions: