test: remove //nolint:govet comments

[alexandear]

This PR refactors the tests for noCopy structs, eliminating the need for //nolint:govet comments.

govet raises lint issues in tests on the reflect.DeepEqual(h1, h2) line where h1, h2 are of type Header. This is because Header contains the special field noCopy, which triggers govet. To appease govet, we can pass pointers to reflect.DeepEqual(&h1, &h2). According to the documentation, we can do this without breaking tests because "Pointer values are deeply equal if they are equal using Go's == operator or if they point to deeply equal values."

[erikdubbelboer]

Thanks!