Update istio/install-cni Docker tag to v1.19.7

This MR contains the following updates:

Package	Type	Update	Change
istio/install-cni		patch	1.19.6 -> 1.19.7
istio/install-cni	ironbank-docker	patch	1.19.6-distroless -> 1.19.7-distroless
istio/install-cni	stage	patch	1.19.6-distroless -> 1.19.7-distroless

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