CL 379116 changes the format of the error this checker is looking for.
Update it to handle both the old and new form.
Change-Id: I91668e4fcbe203a9028d07b780fd17e9758fc838
Reviewed-on: https://go-review.googlesource.com/c/tools/+/379174
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>