Update registry1.dso.mil/ironbank/google/golang/ubi9/golang-1.21 Docker tag to v1.21.8

This MR contains the following updates:

Package	Type	Update	Change
registry1.dso.mil/ironbank/google/golang/ubi9/golang-1.21 (source)	final	patch	1.21.7 -> 1.21.8

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