Drop support for Go 1.21 in dice example #14291

Job	Run time
lint	2m 25s
test-bench	41s
test-concurrent-safe	4m 13s
test-race	2m 15s
test-coverage	56s
compatibility-test (1.23.0, ubuntu-latest, 386)	1m 18s
compatibility-test (1.23.0, ubuntu-latest, amd64)	28s
compatibility-test (1.23.0, macos-13, amd64)	2m 33s
compatibility-test (1.23.0, macos-latest, arm64)	36s
compatibility-test (1.23.0, windows-latest, 386)	2m 12s
compatibility-test (1.23.0, windows-latest, amd64)	3m 42s
compatibility-test (1.23.0, actuated-arm64-2cpu-8gb, arm64)	2m 7s
compatibility-test (~1.22.5, ubuntu-latest, 386)	1m 12s
compatibility-test (~1.22.5, ubuntu-latest, amd64)	26s
compatibility-test (~1.22.5, macos-13, amd64)	1m 55s
compatibility-test (~1.22.5, macos-latest, arm64)	46s
compatibility-test (~1.22.5, windows-latest, 386)	3m 50s
compatibility-test (~1.22.5, windows-latest, amd64)	1m 37s
compatibility-test (~1.22.5, actuated-arm64-2cpu-8gb, arm64)	2m 0s
codecov	9s
test-compatibility	1s
	35m 22s

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