[vm] Remove underscore in copyright header
[vm] Remove underscore in copyright header

TEST=comment only change
Change-Id: I4e943046b67ed9708bc95bf72890c65ea49167c3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/238602
Reviewed-by: Alexander Aprelev <dfb74c35a357c2059971a4bf7fe26b6a7c18085d@google.com>
Reviewed-by: Zach Anderson <9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com>
Commit-Queue: Zach Anderson <9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk