[resultui] fix missing copyright header in signin.ts
[resultui] fix missing copyright header in signin.ts

R=7f5d2f4f6ce87649784e35ad551490ab8d89e8eb@google.com, orodley@google.com

Change-Id: Ib7504f79165e77621a355f28ff53a1fff2193213
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2437531
Auto-Submit: Weiwei Lin <968518a24f41fef00b747498600e52b792d06ae0@google.com>
Reviewed-by: Quang Minh Tuan Nguyen <7f5d2f4f6ce87649784e35ad551490ab8d89e8eb@google.com>
Commit-Queue: Weiwei Lin <968518a24f41fef00b747498600e52b792d06ae0@google.com>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go