Update ghcr.io/fluxcd/kustomize-controller Docker tag to v0.31.0

This MR contains the following updates:

Package	Update	Change
ghcr.io/fluxcd/kustomize-controller	minor	v0.30.0 -> v0.31.0

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Release Notes

fluxcd/kustomize-controller

v0.31.0

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CHANGELOG

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