Update ironbank/opensource/istio/operator Docker tag to v1.13.1

This MR contains the following updates:

Package	Update	Change
ironbank/opensource/istio/operator	minor	1.11.5 -> 1.13.1

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CHANGELOG.md

@@ -3,6 +3,12 @@
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
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+## [1.13.1-bb.0]
+### Changed
+- Updated kptfile
+- Accepted reasonable changes made by `kpt pkg update` in Chart.yaml, values.yaml, deployment.yaml and gen-operator.yaml
+- Bumped version to `1.13.1-bb.0`
+
 ## [1.11.5-bb.1]
 ### Changed
 - Update Chart.yaml to follow new standardization for release automation