Update quay.io/skupper/config-sync Docker tag to v1.6.0

This MR contains the following updates:

Package	Type	Update	Change
quay.io/skupper/config-sync		minor	1.5.3 -> 1.6.0
quay.io/skupper/config-sync	ironbank-docker	minor	1.5.3 -> 1.6.0
quay.io/skupper/config-sync	stage	minor	1.5.3 -> 1.6.0

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