docs: Replace code of conduct with CNCF COC reference #7332

Job	Run time
docs	28s
image_tags	1s
gomod	53s
lint	3m 48s
test (test)	11m 21s
test (integration-test)	7m 58s
build (controller)	2m 27s
test (helm-test)	3m 11s
build (kanctl)	2m 24s
reno_lint	38s
build (kando)	2m 19s
release	0s
release_example_docker_images	0s
	35m 28s

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