Caught early by the improved vet check gated behind the 1.26 language
version combined with a tiplang builder that tests with 1.26 language
version.

Change-Id: Ie41542014acbbf24464111bd8dabb040ab0a0dea
Cq-Include-Trybots: luci.golang.try:x_oauth2-gotip-linux-amd64-tiplang
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/725240
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Sean Liao <sean@liao.dev>