Security: update go toolchain to 1.21.5 #687

Job	Run time
docker-build	36s
build (linux, amd64)	36s
build (linux, 386)	34s
lint	57s
test	6m 30s
build (linux, arm)	33s
build (linux, arm64)	39s
build (darwin, amd64)	44s
build (darwin, arm64)	42s
build (windows, amd64)	36s
build (windows, 386)	34s
build (windows, arm)	34s
build (windows, arm64)	34s
integration-test-clientside (v0.13.2)	2m 5s
integration-test-serverside (f0023141ec429d912e329665f937d05b178a3fee)	1m 57s
analyze	2m 19s
	20m 30s

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