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)
(cd maintner/cmd/maintserve && go get go@1.26.0 && go mod tidy)

Change-Id: Iba120f019430fc2e387259690c2795c454e5dde1
Reviewed-on: https://go-review.googlesource.com/c/build/+/817742
Reviewed-by: Carlos Amedee <carlos@golang.org>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>

go.mod

diff --git a/go.mod b/go.mod
index 276e351..0a84c5a 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module golang.org/x/build
 
-go 1.25.0
+go 1.26.0
 
 require (
 	cloud.google.com/go/bigquery v1.74.0

maintner/cmd/maintserve/go.mod

diff --git a/maintner/cmd/maintserve/go.mod b/maintner/cmd/maintserve/go.mod
index c932ce5..7467e5b 100644
--- a/maintner/cmd/maintserve/go.mod
+++ b/maintner/cmd/maintserve/go.mod
@@ -1,6 +1,6 @@
 module golang.org/x/build/maintner/cmd/maintserve
 
-go 1.25.0
+go 1.26.0
 
 require (
 	dmitri.shuralyov.com/app/changes v0.0.0-20191223015216-e22f40b36873