bump helm chart version to 0.20.0 (#248)

## Summary
- Bumps the `temporal-worker-controller` Helm chart version from
`0.19.0` to `0.20.0` to reflect the latest helm chart version which was
released.

## Test plan
- [ ] Verify the Helm chart publishes correctly with version `0.20.0`

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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Shivs11

helm/temporal-worker-controller/Chart.yaml

@@ -2,5 +2,5 @@ apiVersion: v2
 name: temporal-worker-controller
 description: A Helm chart for the Temporal Worker Controller
 type: application
-version: 0.19.0
+version: 0.20.0
 appVersion: 1.3.1