Update golang Docker tag to v1.21.6

This MR contains the following updates:

Package	Type	Update	Change
golang	image	patch	1.21.3-alpine3.18 -> 1.21.6-alpine3.18
golang	final	patch	1.21.3-alpine3.18 -> 1.21.6-alpine3.18
golang		patch	1.21.3 -> 1.21.6

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Release Notes

golang/go (golang)

v1.21.6

Compare Source

v1.21.5

Compare Source

v1.21.4

Compare Source

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