[BuildPage] Update banner for switch day
[BuildPage] Update banner for switch day

Bug:1150146
Change-Id: I1e65e9b4ba3d31ae6a75b7dacd7fd88f0e629d89
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2545906
Commit-Queue: Quang Minh Tuan Nguyen <7f5d2f4f6ce87649784e35ad551490ab8d89e8eb@google.com>
Auto-Submit: Quang Minh Tuan Nguyen <7f5d2f4f6ce87649784e35ad551490ab8d89e8eb@google.com>
Reviewed-by: Weiwei Lin <968518a24f41fef00b747498600e52b792d06ae0@google.com>

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