go.mod: update golang.org/x dependencies

Update golang.org/x dependencies to their latest tagged versions.
Once this CL is submitted, and post-submit testing succeeds on all
first-class ports across all supported Go versions, this repository
will be tagged with its next minor version.

Change-Id: I6b389549fe4bc53a62cb383c5fb10156ccfcffba
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/507840
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Gopher Robot <gobot@golang.org>
Auto-Submit: Gopher Robot <gobot@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

go.mod

@@ -11,6 +11,6 @@ require (
 require (
 	cloud.google.com/go/compute v1.20.1 // indirect
 	github.com/golang/protobuf v1.5.3 // indirect
-	golang.org/x/net v0.11.0 // indirect
+	golang.org/x/net v0.12.0 // indirect
 	google.golang.org/protobuf v1.31.0 // indirect
 )