Adding OpenSearch 2.0 to the test matrix (opensearch-project#168)

Signed-off-by: Vacha Shah <vachshah@amazon.com>

Author: VachaShah

.github/workflows/integration.yml

@@ -22,6 +22,7 @@ jobs:
           - { opensearch_version: 1.2.4 }
           - { opensearch_version: 1.3.0 }
           - { opensearch_version: 1.3.1 }
+          - { opensearch_version: 2.0.0 }
 
     steps:
       - name: Checkout