go.mod: ignore cyclic dependency for tagging

Followup to CL 439295; let's try tagging indirect deps too.

For golang/go#48523.

Change-Id: I35c6b8a3ad382b585c0042888abf085e053ef8fb
Reviewed-on: https://go-review.googlesource.com/c/text/+/442517
Auto-Submit: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>

go.mod

@@ -4,7 +4,7 @@ require golang.org/x/tools v0.1.12 // tagx:ignore
 
 require (
 	golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 // indirect
-	golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f // indirect
+	golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f // indirect tagx:ignore
 )
 
 go 1.17