canary: bump golang from 1.21rc4 to 1.21 in /dependabot/docker/go #171

Job	Run time
CI matrix / Assert PR branch is ahead	3s
Makefile / Assert PR branch is ahead	3s
CI matrix / Build codebase (go-ci-oldstable, false)	1m 34s
CI matrix / Build codebase (go-ci-stable, false)	1m 13s
CI matrix / Build codebase (go-ci-unstable, true)	1m 17s
CI matrix / Lint codebase (go-ci-oldstable, false)	1m 42s
CI matrix / Lint codebase (go-ci-stable, false)	1m 41s
CI matrix / Lint codebase (go-ci-unstable, true)	1m 20s
CI matrix / Run tests (go-ci-oldstable, false)	1m 22s
CI matrix / Run tests (go-ci-stable, false)	1m 29s
CI matrix / Run tests (go-ci-unstable, true)	1m 20s
CI matrix / Optional Linting / Assert PR branch is ahead	5s
Makefile / Build codebase using Makefile quick recipe	1m 40s
Makefile / Lint codebase using Makefile	1m 48s
Makefile / Build codebase using Makefile all recipe	0s
CI matrix / Optional Linting / Lint codebase using optional linters (go-ci-oldstable, true)	1m 20s
CI matrix / Optional Linting / Lint codebase using optional linters (go-ci-stable, true)	1m 22s
CI matrix / Optional Linting / Lint codebase using optional linters (go-ci-unstable, true)	1m 34s
	20m 53s

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