Remove license headers from generated code

[fehguy]

Per this discussion:

#2963 (comment)

We should remove the license header from all generated files. The license of the generated files is entirely up to the creator of them, and is not subject to the parent project's licensing choice.

[wing328]

@fehguy I'll work on it this weekend.

[fehguy]

Thanks, I can help as well

[wing328]

Closed via the following PRs:

#4200
#4199
#4197