Enable linter `unparam` for test files #7071

Job	Run time
gomod	55s
docs	29s
image_tags	1s
reno_lint	40s
test (test)	11m 27s
lint	3m 35s
test (integration-test)	7m 59s
build (controller)	2m 27s
test (helm-test)	3m 3s
build (kanctl)	2m 24s
build (kando)	2m 13s
release	0s
release_example_docker_images	0s
	35m 13s

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