Tests

Bump alpine from 3.20.3 to 3.21.0 #430

Job	Run time
build-and-test	2m 24s
lint	1m 45s
versions	1s
copyright / validate	4s
go-checks / Check that code matches gofumpt	23s
go-checks / Check that go.mod and go.sum are tidy	12s
vault:1.18.1 kind:1.31.2	6m 5s
vault:1.18.1 kind:1.30.6	5m 12s
vault:1.17.6 kind:1.31.2	5m 53s
vault:1.18.1 kind:1.29.10	6m 3s
vault:1.16.3 kind:1.31.2	5m 57s
vault:1.18.1 kind:1.28.15	4m 55s
vault:1.18.1 kind:1.27.16	5m 3s
	43m 57s

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