fix: Add env variables to values.yaml, values.schema.json and deployment.yaml

[karinajex1827]

What does this MR do?

This MR adds missing variables GATEWAY_SYSTEM_NAMESPACE and GATEWAY_SYSTEM_NAME to values.yaml and deployment.yaml.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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