Update istio/operator Docker tag to v1.16.3

This MR contains the following updates:

Package	Type	Update	Change
istio/operator	ironbank-docker	patch	1.16.2 -> 1.16.3
istio/operator		patch	1.16.2 -> 1.16.3
istio/operator	stage	patch	1.16.2 -> 1.16.3

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