go.mod: ignore cyclic dependency for tagging

tools and text have a cyclic dependency, which needs to be broken during
the upgrading/tagging process. This direction is due to
message/pipeline, which is marked as "IN DEVELOPMENT", so I think it's
less important to keep it up to date.

For golang/go#48523.

Change-Id: Ic4cdfd05628649035eee8a37e662cf22827c705b
Reviewed-on: https://go-review.googlesource.com/c/text/+/439295
Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

go.mod

@@ -1,6 +1,6 @@
 module golang.org/x/text
 
-require golang.org/x/tools v0.1.12
+require golang.org/x/tools v0.1.12 // tagx:ignore
 
 require (
 	golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 // indirect