fix: correct db2 test credentials to match compose file

Author: iawanish

tests/core/engine_adapter/integration/config.yaml

@@ -219,14 +219,13 @@ gateways:
       type: db2
       host: {{ env_var('DOCKER_HOSTNAME', 'localhost') }}
       port: {{ env_var('DB2_PORT', '50001') }}
-      database: {{ env_var('DB2_DATABASE', 'testdb') }}
+      database: {{ env_var('DB2_DATABASE', 'TESTDB') }}
       username: {{ env_var('DB2_USERNAME', 'db2inst1') }}
-      password: {{ env_var('DB2_PASSWORD', 'password') }}
+      password: {{ env_var('DB2_PASSWORD', 'db2inst1') }}
       db2_schema: {{ env_var('DB2_SCHEMA', 'DB2INST1') }}
       check_import: false
     state_connection:
       type: duckdb
-      # ... keep whatever was here before ...
 
   inttest_fabric:
     connection: