all: upgrade go directive to at least 1.26.0 [generated]

By now Go 1.27.0 has been released, and Go 1.25 is no longer supported
per the Go Release Policy (see https://go.dev/doc/devel/release#policy).

See https://go.dev/doc/godebug#go-126 for GODEBUG setting changes
relevant to Go 1.26.

For golang/go#69095.

[git-generate]
(cd . && go get go@1.26.0 && go mod tidy)

Change-Id: I1bdbd99000a6eed1a9c85d7f58c5597272bdc94c
Reviewed-on: https://go-review.googlesource.com/c/review/+/817860
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: David Chase <drchase@google.com>
diff --git a/go.mod b/go.mod
index 58066cc..b76be01 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module golang.org/x/review
 
-go 1.25.0
+go 1.26.0