Update license header for gofmt with Go 1.19

[ckadner]

The Go 1.19 Release Notes mention a change to gofmt that causes it to reformat godoc comments.

Because the copyright headers are placed directly above the package declaration, gofmt for 1.19 is interpreting them as godocs and formatting them. (I verified that adding a blank line above the package directive prevents the change.)

The effect that the change to gofmt has on our code will have to be addressed, but I'd prefer that it happens in a separate PR.

Originally posted by @tjohnson31415 in #340 (comment)