Build Image: Bump atc0005/go-ci from go-ci-unstable-build-v0.21.13 to go-ci-unstable-build-v0.21.15 in /dependabot/docker/builds #486

Job	Run time
Makefile / Assert PR branch is ahead	4s
CI matrix / Assert PR branch is ahead	5s
Makefile / Build codebase using Makefile quick recipe	36s
Makefile / Lint codebase using Makefile	0s
Makefile / Build codebase using Makefile all recipe	0s
CI matrix / Lint codebase (go-ci-oldstable, false)	37s
CI matrix / Lint codebase (go-ci-stable, false)	33s
CI matrix / Evaluate loopvar scoping changes	26s
CI matrix / Lint codebase (go-ci-unstable, true)	32s
CI matrix / Run tests (go-ci-oldstable, false)	30s
CI matrix / Run tests (go-ci-stable, false)	31s
CI matrix / Run tests (go-ci-unstable, true)	27s
CI matrix / Build codebase (go-ci-oldstable, false)	22s
CI matrix / Build codebase (go-ci-stable, false)	26s
CI matrix / Build codebase (go-ci-unstable, true)	30s
CI matrix / Optional Linting / Assert PR branch is ahead	6s
CI matrix / Optional Linting / Lint codebase using optional linters (go-ci-oldstable, true)	28s
CI matrix / Optional Linting / Lint codebase using optional linters (go-ci-stable, true)	37s
CI matrix / Optional Linting / Lint codebase using optional linters (go-ci-unstable, true)	28s
	7m 18s

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