Update rook/ceph Docker tag to v1.11.8

This MR contains the following updates:

Package	Type	Update	Change
rook/ceph	ironbank-docker	patch	v1.11.7 -> v1.11.8
rook/ceph		patch	v1.11.7 -> v1.11.8
rook/ceph	stage	patch	v1.11.7 -> v1.11.8

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